Encoder, decoder, encoding method, and decoding method

ABSTRACT

An encoder which includes circuitry and memory. Using the memory, the circuitry generates a list which includes candidates for a first motion vector for a first partition. The list has a maximum list size and an order of the candidates, and at least one of the maximum list size or the order of the candidates is dependent on at least one of a partition size or a partition shape of the first partition. The circuitry selects the first motion vector from the candidates included in the list; encodes an index indicating the first motion vector among the candidates in the list into the bitstream based on the maximum list size; and generates the predicted image for the first partition using the first motion vector.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. continuation application of PCT InternationalPatent Application Number PCT/JP2019/019072 filed on May 14, 2019,claiming the benefit of priority of U.S. Provisional Patent ApplicationNo. 62/672,801 filed on May 17, 2018, the entire contents of which arehereby incorporated by reference.

BACKGROUND 1. Technical Field

The present disclosure relates to an encoder, etc. for encoding a videointo a bitstream using a predicted image.

2. Description of the Related Art

Conventionally, there has been H. 265 also referred to as (ISO/IEC23008-2 HEVC)/HEVC (High Efficiency Video Coding) as a standard forencoding a video.

SUMMARY

An encoder according to an aspect of the present disclosure is anencoder which encodes a video into a bitstream using a predicted image,and which includes circuitry and memory. Using the memory, the circuitrygenerates a list which includes a plurality of candidates for a firstmotion vector for a first partition in the video, and in which theplurality of candidates includes a candidate which is derived from asecond motion vector of a second partition different from the firstpartition in the video. The list has a maximum list size and an order ofthe plurality of candidates, and at least one of the maximum list sizeor the order of the plurality of candidates is dependent on at least oneof a partition size or a partition shape of the first partition. Usingthe memory the circuitry: selects the first motion vector from theplurality of candidates included in the list; encodes an indexindicating the first motion vector among the plurality of candidates inthe list into the bitstream based on the maximum list size; andgenerates the predicted image for the first partition using the firstmotion vector.

It is to be noted that these general or specific aspects may beimplemented using a system, an apparatus, a method, an integratedcircuit, a computer program, or a non-transitory computer-readablerecording medium such as a CD-ROM, or any combination of systems,apparatuses, methods, integrated circuits, computer programs, orcomputer-readable recording media.

BRIEF DESCRIPTION OF DRAWINGS

These and other objects, advantages and features of the disclosure willbecome apparent from the following description thereof taken inconjunction with the accompanying drawings that illustrate a specificembodiment of the present disclosure.

FIG. 1 is a block diagram illustrating a functional configuration of anencoder according to Embodiment 1;

FIG. 2 illustrates one example of block splitting according toEmbodiment 1;

FIG. 3 is a chart indicating transform basis functions for eachtransform type;

FIG. 4A illustrates one example of a filter shape used in ALF;

FIG. 4B illustrates another example of a filter shape used in ALF;

FIG. 4C illustrates another example of a filter shape used in ALF;

FIG. 5A illustrates 67 intra prediction modes used in intra prediction;

FIG. 5B is a flow chart for illustrating an outline of a predictionimage correction process performed via OBMC processing;

FIG. 5C is a conceptual diagram for illustrating an outline of aprediction image correction process performed via OBMC processing;

FIG. 5D illustrates one example of FRUC;

FIG. 6 is for illustrating pattern matching (bilateral matching) betweentwo blocks along a motion trajectory;

FIG. 7 is for illustrating pattern matching (template matching) betweena template in the current picture and a block in a reference picture;

FIG. 8 is for illustrating a model assuming uniform linear motion;

FIG. 9A is for illustrating deriving a motion vector of each sub-blockbased on motion vectors of neighboring blocks;

FIG. 9B is for illustrating an outline of a process for deriving amotion vector via merge mode;

FIG. 9C is a conceptual diagram for illustrating an outline of DMVRprocessing;

FIG. 9D is for illustrating an outline of a prediction image generationmethod using a luminance correction process performed via LICprocessing;

FIG. 10 is a block diagram illustrating a functional configuration of adecoder according to Embodiment 1;

FIG. 11 is a flow chart indicating a first aspect of inter predictionperformed by an encoder according to Embodiment 1;

FIG. 12 is a flow chart indicating the first aspect of inter predictionperformed by a decoder according to Embodiment 1;

FIG. 13 is a conceptual diagram illustrating examples of maximum numbersof motion vector candidates which are dependent on partition sizesaccording to Embodiment 1;

FIG. 14 is a conceptual diagram illustrating other examples of maximumnumbers of motion vector candidates which are dependent on partitionsizes according to Embodiment 1;

FIG. 15 is a flow chart indicating a second aspect of inter predictionperformed by the encoder according to Embodiment 1;

FIG. 16 is a flow chart indicating the second aspect of inter predictionperformed by the decoder according to Embodiment 1;

FIG. 17 is a conceptual diagram illustrating examples of maximum numbersof motion vector candidates which are dependent on partition sizesaccording to Embodiment 1;

FIG. 18 is a conceptual diagram illustrating examples of maximum numbersof motion vector candidates which are dependent on partition shapesaccording to Embodiment 1;

FIG. 19 is a flow chart indicating a third aspect of inter predictionperformed by the encoder according to Embodiment 1;

FIG. 20 is a flow chart indicating the third aspect of inter predictionperformed by the decoder according to Embodiment 1;

FIG. 21 is a conceptual diagram illustrating examples of maximum numbersof motion vector candidates which are dependent on partition sizesaccording to Embodiment 1;

FIG. 22 is a conceptual diagram illustrating examples of maximum numbersof motion vector candidates which are dependent on partition sizesaccording to Embodiment 1;

FIG. 23 is a flow chart indicating a fourth aspect of inter predictionperformed by the encoder according to Embodiment 1;

FIG. 24 is a flow chart indicating the fourth aspect of inter predictionperformed by the decoder according to Embodiment 1;

FIG. 25 is a conceptual diagram illustrating example orders ofcandidates which are dependent on partition sizes according toEmbodiment 1;

FIG. 26 is a conceptual diagram illustrating example orders ofcandidates which are dependent on partition shapes according toEmbodiment 1;

FIG. 27 is a block diagram illustrating an example of mounting theencoder according to Embodiment 1;

FIG. 28 is a flow chart indicating an example of an operation performedby the encoder according to Embodiment 1;

FIG. 29 is a block diagram illustrating an example of mounting thedecoder according to Embodiment 1;

FIG. 30 is a flow chart indicating an example of an operation performedby the decoder according to Embodiment 1;

FIG. 31 illustrates an overall configuration of a content providingsystem for implementing a content distribution service;

FIG. 32 illustrates one example of an encoding structure in scalableencoding;

FIG. 33 illustrates one example of an encoding structure in scalableencoding;

FIG. 34 illustrates an example of a display screen of a web page;

FIG. 35 illustrates an example of a display screen of a web page;

FIG. 36 illustrates one example of a smartphone; and

FIG. 37 is a block diagram illustrating a configuration example of asmartphone.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(Underlying Knowledge Forming Basis of the Present Disclosure)

For example, an encoder encodes a video block by block. The encoder mayuse inter prediction or intra prediction when encoding the video blockby block. When using inter prediction to encode a current block to beprocessed, the encoder identifies a reference block and generates apredicted image of the current block by referring to a reference block.The encoder then encodes a difference image between the predicted imageof the current block and the original image of the current block,thereby reducing the code amount.

In addition, a decoder decodes a difference image when decoding a video.The decoder then generates a predicted image of a current block to beprocessed by referring to a reference block and adds the predicted imageand the difference image to reconstruct the original image. In this way,the decoder is capable of decoding the video.

In addition, for example, the encoder and the decoder generate a motionvector candidate list for the current block using a common method, andselect a motion vector for the current block from the motion vectorcandidate list. The encoder and the decoder then generate a predictedvalue of the current block using the motion vector for the currentblock.

In addition, the encoder encodes an index indicating the motion vectorfor the current block in the motion vector candidate list for thecurrent block. In addition, the decoder decodes an index indicating themotion vector for the current block in the motion vector candidate listfor the current block.

In this way, the encoder and the decoder are capable of selecting thesame motion vector from the motion vector candidate list generated usingthe common method, and generating the same predicted image using thesame motion vector. The encoder and the decoder are then capable ofencoding and decoding the video appropriately using the same predictedimage.

However, if information for prediction is not configured appropriately,the code amount may increase.

For example, the code amount of an index indicating a motion vector fora current block to be processed in a motion vector candidate list isdependent on a maximum list size of the motion vector candidate list. Inaddition, the code amount of the index indicating the motion vector forthe current block is dependent on the position of the motion vector forthe current block in the motion vector candidate list. For example, thecode amount of the index indicating the motion vector for the currentblock in the motion vector candidate list is dependent on the order ofcandidates in the motion vector candidate list.

Accordingly, the code amount of the index indicating the motion vectorfor the current block in the motion vector candidate list may increasedepending on the maximum list size of the motion vector candidate listand the order of candidates in the motion vector candidate list.

In view of this, for example, an encoder according to an aspect of thepresent disclosure is an encoder which encodes a video into a bitstreamusing a predicted image, and which includes circuitry and memory. Usingthe memory, the circuitry generates a list which includes a plurality ofcandidates for a first motion vector for a first partition in the video,and in which the plurality of candidates includes a candidate which isderived from a second motion vector of a second partition different fromthe first partition in the video. The list has a maximum list size andan order of the plurality of candidates, and at least one of the maximumlist size or the order of the plurality of candidates is dependent on atleast one of a partition size or a partition shape of the firstpartition. Using the memory, the circuitry: selects the first motionvector from the plurality of candidates included in the list; encodes anindex indicating the first motion vector among the plurality ofcandidates in the list into the bitstream based on the maximum listsize; and generates the predicted image for the first partition usingthe first motion vector.

In this way, the encoder is capable of generating the motion vectorcandidate list based on the maximum list size or the order of thecandidates which is dependent on the partition size or the partitionshape. Accordingly, the encoder is capable of generating the appropriatecandidate list based on the partition size or the partition shape. Inother words, the encoder is capable of appropriately configuringinformation for prediction. Accordingly, the encoder is capable ofcontributing to reduction in code amount.

In addition, for example, the maximum list size is a first list sizewhen the partition size is a first partition size, and the maximum listsize is a second list size larger than the first list size when thepartition size is a second partition size smaller than the firstpartition size.

In this way, the encoder is capable of selecting the appropriate motionvector from among the large number of motion vector candidates for thesmall partition. On the other hand, there is the possibility that noappropriate motion vector is included in the large number of motionvector candidates for the large partition. Accordingly, the encoder iscapable of contributing to reduction in code amount of the indexindicating the motion vector by using the motion vector candidate listhaving the small maximum list size for the large partition.

In addition, for example, the maximum list size is a first list sizewhen the partition size is a first partition size, and the maximum listsize is a second list size smaller than the first list size when thepartition size is a second partition size smaller than the firstpartition size.

In this way, the encoder is capable of selecting the appropriate motionvector from among the large number of motion vector candidates for thelarge partition. Accordingly the encoder is capable of simplifying theprocessing and contributing to reduction in code amount of the indexindicating the motion vector by using the motion vector candidate listhaving the small maximum list size for the small partition.

In addition, for example, the maximum list size is dependent on thepartition shape, and the partition shape is one of a square, arectangle, and a triangle.

In this way, the encoder is capable of generating the appropriatecandidate list based on the partition shape which is one of a square, arectangle, or a triangle.

In addition, for example, the maximum list size is a first list sizewhen the partition shape is a triangle, and the maximum list size is asecond list size larger than the first list size when the partitionshape is not a triangle.

In this way, the encoder is capable of selecting the appropriate motionvector from among the large number of motion vector candidates for therectangular partition. On the other hand, there is a possibility thatthe number of referable processed partitions is small and the number ofderivable motion vector candidates is small around the triangularpartition. Accordingly, the encoder is capable of contributing toreduction in code amount of the index indicating the motion vector byusing the motion vector candidate list having the small maximum listsize for the triangular partition.

In addition, for example, the maximum list size is a first list sizewhen the partition shape is a square, and the maximum list size is asecond list size larger than the first list size when the partitionshape is not a square.

In this way, the encoder is capable of selecting an appropriate motionvector from among a large number of motion vector candidates for apartition having a complicated shape. Accordingly, the encoder iscapable of simplifying processing and contributing to reduction in codeamount of an index indicating a motion vector by using a motion vectorcandidate list having a small maximum list size for a partition having asimple shape.

In addition, for example, the circuitry: encodes the index using a firstnumber of bits when the maximum list size is a first list size; andencodes the index using a second number of bits larger than the firstnumber of bits when the maximum list size is a second list size largerthan the first list size.

In this way, the encoder is capable of encoding the index using theappropriate number of bits based on the maximum list size.

In addition, for example, the second partition is a partition whichneighbors the first partition.

In this way, the encoder is capable of deriving a candidate for themotion vector for the current partition from a motion vector of apartition that neighbors the current partition. Accordingly, the encoderis capable of appropriately deriving the candidate for the motion vectorfor the current partition from the motion vector that is assumed to besimilar to the motion vector for the current partition.

In addition, for example, a decoder according to an aspect of thepresent disclosure is a decoder which decodes a video from a bitstreamusing a predicted image, and which includes circuitry and memory. Usingthe memory, the circuitry generates a list which includes a plurality ofcandidates for a first motion vector for a first partition in the video,and in which the plurality of candidates includes a candidate which isderived from a second motion vector of a second partition different fromthe first partition in the video. The list has a maximum list size andan order of the plurality of candidates, and at least one of the maximumlist size or the order of the plurality of candidates is dependent on atleast one of a partition size or a partition shape of the firstpartition. Using the memory the circuitry: decodes an index indicatingthe first motion vector among the plurality of candidates in the listfrom the bitstream based on the maximum list size; selects the firstmotion vector from the plurality of candidates in the list using theindex; and generates the predicted image for the first partition usingthe first motion vector.

In this way, the decoder is capable of generating the motion vectorcandidate list based on the maximum list size or the order of thecandidates which is dependent on the partition size or the partitionshape. Accordingly, the decoder is capable of generating the appropriatecandidate list based on the partition size or the partition shape. Inother words, the decoder is capable of appropriately configuringinformation for prediction. Accordingly, the decoder is capable ofcontributing to reduction in code amount.

In addition, for example, the maximum list size is a first list sizewhen the partition size is a first partition size, and the maximum listsize is a second list size larger than the first list size when thepartition size is a second partition size smaller than the firstpartition size.

In this way, the decoder is capable of selecting the appropriate motionvector from among the large number of motion vector candidates for thesmall partition. On the other hand, there is a possibility that noappropriate motion vector is included in the large number of motionvector candidates for the large partition. Accordingly, the decoder iscapable of contributing to reduction in code amount of the indexindicating the motion vector by using the motion vector candidate listhaving the small maximum list size for the large partition.

In addition, for example, the maximum list size is a first list sizewhen the partition size is a first partition size, and the maximum listsize is a second list size smaller than the first list size when thepartition size is a second partition size smaller than the firstpartition size.

In this way, the decoder is capable of selecting the appropriate motionvector from among the large number of motion vector candidates for thelarge partition. On the other hand, the decoder is capable ofsimplifying the processing and contributing to reduction in code amountof the index indicating the motion vector by using the motion vectorcandidate list having the small maximum list size for the smallpartition.

In addition, for example, the maximum list size is dependent on thepartition shape, and the partition shape is one of a square, arectangle, and a triangle.

-   -   In this way, the decoder is capable of generating the        appropriate candidate list based on the partition shape which is        one of a square, a rectangle, or a triangle.

In addition, for example, the maximum list size is a first list sizewhen the partition shape is a triangle, and the maximum list size is asecond list size larger than the first list size when the partitionshape is not a triangle.

In this way, the decoder is capable of selecting the appropriate motionvector from among the large number of motion vector candidates for therectangular partition. On the other hand, there is a possibility thatthe number of referable processed partitions is small and the number ofderivable motion vector candidates is small around the triangularpartition. Accordingly, the decoder is capable of contributing toreduction in code amount of the index indicating the motion vector byusing the motion vector candidate list having the small maximum listsize for the triangular partition.

In addition, for example, the maximum list size is a first list sizewhen the partition shape is a square, and the maximum list size is asecond list size larger than the first list size when the partitionshape is not a square.

In this way, the decoder is capable of selecting an appropriate motionvector from among a large number of motion vector candidates for apartition having a complicated shape. On the other hand, the decoder iscapable of simplifying processing and contributing to reduction in codeamount of an index indicating a motion vector by using a motion vectorcandidate list having a small maximum list size for a partition having asimple shape.

In addition, for example, the circuitry: decodes the index using a firstnumber of bits when the maximum list size is a first list size; anddecodes the index using a second number of bits larger than the firstnumber of bits when the maximum list size is a second list size largerthan the first list size.

In this way, the decoder is capable of decoding the index using theappropriate number of bits based on the maximum list size.

In addition, for example, the second partition is a partition whichneighbors the first partition.

In this way, the decoder is capable of deriving a candidate for themotion vector for the current partition from a motion vector of apartition that neighbors the current partition. Accordingly, the decoderis capable of appropriately deriving the candidate for the motion vectorfor the current partition from the motion vector that is assumed to besimilar to the motion vector for the current partition.

In addition, for example, an encoding method according to an aspect ofthe present disclosure is an encoding method of encoding a video into abitstream using a predicted image. The encoding method includesgenerating a list which includes a plurality of candidates for a firstmotion vector for a first partition in the video, and in which theplurality of candidates includes a candidate which is derived from asecond motion vector of a second partition different from the firstpartition in the video. The list has a maximum list size and an order ofthe plurality of candidates, and at least one of the maximum list sizeor the order of the plurality of candidates is dependent on at least oneof a partition size or a partition shape of the first partition. Theencoding method includes: selecting the first motion vector from theplurality of candidates included in the list; encoding an indexindicating the first motion vector among the plurality of candidates inthe list into the bitstream based on the maximum list size; andgenerating the predicted image for the first partition using the firstmotion vector.

In this way, it is possible to generate the motion vector candidate listbased on the maximum list size or the order of the candidates which isdependent on the partition size or the partition shape. Accordingly, itis possible to generate the appropriate candidate list based on thepartition size or the partition shape. In other words, it is possible toappropriately configure information for prediction. Thus, it is possibleto contribute to reduction in code amount.

In addition, for example, a decoding method according to an aspect ofthe present disclosure is a decoding method of decoding a video from abitstream using a predicted image. The decoding method includesgenerating a list which includes a plurality of candidates for a firstmotion vector for a first partition in the video, and in which theplurality of candidates includes a candidate which is derived from asecond motion vector of a second partition different from the firstpartition in the video. The list has a maximum list size and an order ofthe plurality of candidates, and at least one of the maximum list sizeor the order of the plurality of candidates is dependent on at least oneof a partition size or a partition shape of the first partition. Thedecoding method includes: decoding an index indicating the first motionvector among the plurality of candidates in the list from the bitstreambased on the maximum list size; selecting the first motion vector fromthe plurality of candidates in the list using the index; and generatingthe predicted image for the first partition using the first motionvector.

In this way, the decoder is capable of generating the motion vectorcandidate list based on the maximum list size or the order of thecandidates which is dependent on the partition size or the partitionshape. Accordingly, the decoder is capable of generating the appropriatecandidate list based on the partition size or the partition shape. Inother words, the decoder is capable of appropriately configuringinformation for prediction. Accordingly, the decoder is capable ofcontributing to reduction in code amount.

In addition, for example, an encoder according to an aspect of thepresent disclosure is an encoder which encodes a video into a bitstreamusing a predicted image, and includes a splitter, an intra predictor, aninter predictor, a transformer, a quantizer, and an entropy encoder.

The splitter splits a current picture to be processed included in thevideo in a plurality of blocks. The intra predictor generates thepredicted image for the current block in the current picture using areference image in the current picture. The inter predictor generatesthe predicted image using a reference image in a reference picturedifferent from the current picture.

The transformer transforms a difference image between the predictedimage generated by either the intra predictor or the inter predictor andan image of the current block to generate a plurality of transformcoefficients. The quantizer quantizes the plurality of transformcoefficients to generate a plurality of quantized coefficients. Theentropy encoder encodes the plurality of quantized coefficients into thebitstream.

In addition, the inter predictor generates a list which includes aplurality of candidates for a first motion vector for a first partitionin the video, and in which the plurality of candidates includes acandidate which is derived from a second motion vector of a secondpartition different from the first partition in the video. The list hasa maximum list size and an order of the plurality of candidates, and atleast one of the maximum list size or the order of the plurality ofcandidates is dependent on at least one of a partition size or apartition shape of the first partition. The inter predictor selects thefirst motion vector from the plurality of candidates included in thelist, and encodes an index indicating the first motion vector among theplurality of candidates in the list into the bitstream based on themaximum list size.

In addition, the entropy encoder encodes an index indicating the firstmotion vector among the plurality of candidates in the list into thebitstream based on the maximum list size. In addition, the interpredictor generates the predicted image for the first partition usingthe first motion vector.

In addition, for example, a decoder according to an aspect of thepresent disclosure is a decoder which decodes a video from a bitstreamusing a predicted image, and includes an entropy decoder, an inversequantizer, an inverse transformer, an intra predictor, an interpredictor, and an adder (reconstructor).

The entropy decoder decodes a plurality of quantized coefficients fromthe bitstream. The inverse quantizer inverse quantizes the plurality ofquantized coefficients to obtain a plurality of transform coefficients.The inverse transformer inverse transforms the plurality of transformcoefficients to obtain a difference image.

The intra predictor generates the predicted image for a current block tobe processed in a current picture using a reference image in the currentpicture included in the video. The inter predictor generates thepredicted image using a reference image in a reference picture differentfrom the current picture. The adder adds the predicted image generatedby either the intra predictor or the inter predictor and the differenceimage to reconstruct an image of the current block.

In addition, the inter predictor generates a list which includes aplurality of candidates for a first motion vector for a first partitionin the video, and in which the plurality of candidates includes acandidate which is derived from a second motion vector of a secondpartition different from the first partition in the video. The list hasa maximum list size and an order of the plurality of candidates, and atleast one of the maximum list size or the order of the plurality ofcandidates is dependent on at least one of a partition size or apartition shape of the first partition.

In addition, the entropy decoder decodes an index indicating the firstmotion vector among the plurality of candidates in the list from thebitstream based on the maximum list size. In addition, the interpredictor selects the first motion vector from the plurality ofcandidates in the list using the index, and generates the predictedimage for the first partition using the first motion vector.

Furthermore, these general or specific aspects may be implemented usinga system, an apparatus, a method, an integrated circuit, a computerprogram, or a non-transitory computer-readable recording medium such asa CD-ROM, or any combination of systems, apparatuses, methods,integrated circuits, computer programs, or computer-readable recordingmedia.

Hereinafter, embodiments will be described with reference to thedrawings.

It is to be noted that the embodiments described below each indicates ageneral or specific example. The numerical values, shapes, materials,constituent elements, the arrangement and connection of the constituentelements, steps, order of the steps, etc., indicated in the followingembodiment and variations are mere examples, and therefore are notintended to limit the scope of the claims. Therefore, among theconstituent elements in the following embodiments, those not recited inany of the independent claims defining the broadest inventive conceptsare described as optional components.

Embodiment 1

First, an outline of Embodiment 1 will be presented. Embodiment 1 is oneexample of an encoder and a decoder to which the processes and/orconfigurations presented in subsequent description of aspects of thepresent disclosure are applicable. Note that Embodiment 1 is merely oneexample of an encoder and a decoder to which the processes and/orconfigurations presented in the description of aspects of the presentdisclosure are applicable. The processes and/or configurations presentedin the description of aspects of the present disclosure can also beimplemented in an encoder and a decoder different from those accordingto Embodiment 1.

When the processes and/or configurations presented in the description ofaspects of the present disclosure are applied to Embodiment 1, forexample, any of the following may be performed.

(1) regarding the encoder or the decoder according to Embodiment 1,among components included in the encoder or the decoder according toEmbodiment 1, substituting a component corresponding to a componentpresented in the description of aspects of the present disclosure with acomponent presented in the description of aspects of the presentdisclosure;

(2) regarding the encoder or the decoder according to Embodiment 1,implementing discretionary changes to functions or implemented processesperformed by one or more components included in the encoder or thedecoder according to Embodiment 1, such as addition, substitution, orremoval, etc., of such functions or implemented processes, thensubstituting a component corresponding to a component presented in thedescription of aspects of the present disclosure with a componentpresented in the description of aspects of the present disclosure;

(3) regarding the method implemented by the encoder or the decoderaccording to Embodiment 1, implementing discretionary changes such asaddition of processes and/or substitution, removal of one or more of theprocesses included in the method, and then substituting a processescorresponding to a process presented in the description of aspects ofthe present disclosure with a process presented in the description ofaspects of the present disclosure;

(4) combining one or more components included in the encoder or thedecoder according to Embodiment 1 with a component presented in thedescription of aspects of the present disclosure, a component includingone or more functions included in a component presented in thedescription of aspects of the present disclosure, or a component thatimplements one or more processes implemented by a component presented inthe description of aspects of the present disclosure;

(5) combining a component including one or more functions included inone or more components included in the encoder or the decoder accordingto Embodiment 1, or a component that implements one or more processesimplemented by one or more components included in the encoder or thedecoder according to Embodiment 1 with a component presented in thedescription of aspects of the present disclosure, a component includingone or more functions included in a component presented in thedescription of aspects of the present disclosure, or a component thatimplements one or more processes implemented by a component presented inthe description of aspects of the present disclosure;

(6) regarding the method implemented by the encoder or the decoderaccording to Embodiment 1, among processes included in the method,substituting a process corresponding to a process presented in thedescription of aspects of the present disclosure with a processpresented in the description of aspects of the present disclosure; and

(7) combining one or more processes included in the method implementedby the encoder or the decoder according to Embodiment 1 with a processpresented in the description of aspects of the present disclosure.

Note that the implementation of the processes and/or configurationspresented in the description of aspects of the present disclosure is notlimited to the above examples. For example, the processes and/orconfigurations presented in the description of aspects of the presentdisclosure may be implemented in a device used for a purpose differentfrom the moving picture/picture encoder or the moving picture/picturedecoder disclosed in Embodiment 1. Moreover, the processes and/orconfigurations presented in the description of aspects of the presentdisclosure may be independently implemented. Moreover, processes and/orconfigurations described in different aspects may be combined.

[Encoder Outline]

First, the encoder according to Embodiment 1 will be outlined. FIG. 1 isa block diagram illustrating a functional configuration of encoder 100according to Embodiment 1. Encoder 100 is a moving picture/pictureencoder that encodes a moving picture/picture block by block.

As illustrated in FIG. 1, encoder 100 is a device that encodes a pictureblock by block, and includes splitter 102, subtractor 104, transformer106, quantizer 108, entropy encoder 110, inverse quantizer 112, inversetransformer 114, adder 116, block memory 118, loop filter 120, framememory 122, intra predictor 124, inter predictor 126, and predictioncontroller 128.

Encoder 100 is realized as, for example, a generic processor and memory.In this case, when a software program stored in the memory is executedby the processor, the processor functions as splitter 102, subtractor104, transformer 106, quantizer 108, entropy encoder 110, inversequantizer 112, inverse transformer 114, adder 116, loop filter 120,intra predictor 124, inter predictor 126, and prediction controller 128.Alternatively, encoder 100 may be realized as one or more dedicatedelectronic circuits corresponding to splitter 102, subtractor 104,transformer 106, quantizer 108, entropy encoder 110, inverse quantizer112, inverse transformer 114, adder 116, loop filter 120, intrapredictor 124, inter predictor 126, and prediction controller 128.

Hereinafter, each component included in encoder 100 will be described.

[Splitter]

Splitter 102 splits each picture included in an input moving pictureinto blocks, and outputs each block to subtractor 104. For example,splitter 102 first splits a picture into blocks of a fixed size (forexample, 128×128). The fixed size block is also referred to as codingtree unit (CTU). Splitter 102 then splits each fixed size block intoblocks of variable sizes (for example, 64×64 or smaller), based onrecursive quadtree and/or binary tree block splitting. The variable sizeblock is also referred to as a coding unit (CU), a prediction unit (PU),or a transform unit (TU). Note that in this embodiment, there is no needto differentiate between CU, PU, and TU; all or some of the blocks in apicture may be processed per CU, PU, or TU.

FIG. 2 illustrates one example of block splitting according toEmbodiment 1. In FIG. 2, the solid lines represent block boundaries ofblocks split by quadtree block splitting, and the dashed lines representblock boundaries of blocks split by binary tree block splitting.

Here, block 10 is a square 128×128 pixel block (128×128 block). This128×128 block 10 is first split into four square 64×64 blocks (quadtreeblock splitting).

The top left 64×64 block is further vertically split into two rectangle32×64 blocks, and the left 32×64 block is further vertically split intotwo rectangle 16×64 blocks (binary tree block splitting). As a result,the top left 64×64 block is split into two 16×64 blocks 11 and 12 andone 32×64 block 13.

The top right 64×64 block is horizontally split into two rectangle 64×32blocks 14 and 15 (binary tree block splitting).

The bottom left 64×64 block is first split into four square 32×32 blocks(quadtree block splitting). The top left block and the bottom rightblock among the four 32×32 blocks are further split. The top left 32×32block is vertically split into two rectangle 16×32 blocks, and the right16×32 block is further horizontally split into two 16×16 blocks (binarytree block splitting). The bottom right 32×32 block is horizontallysplit into two 32×16 blocks (binary tree block splitting). As a result,the bottom left 64×64 block is split into 16×32 block 16, two 16×16blocks 17 and 18, two 32×32 blocks 19 and 20, and two 32×16 blocks 21and 22.

The bottom right 64×64 block 23 is not split.

As described above, in FIG. 2, block 10 is split into 13 variable sizeblocks 11 through 23 based on recursive quadtree and binary tree blocksplitting. This type of splitting is also referred to as quadtree plusbinary tree (QTBT) splitting.

Note that in FIG. 2, one block is split into four or two blocks(quadtree or binary tree block splitting), but splitting is not limitedto this example. For example, one block may be split into three blocks(ternary block splitting). Splitting including such ternary blocksplitting is also referred to as multi-type tree (MBT) splitting.

[Subtractor]

Subtractor 104 subtracts a prediction signal (prediction sample) from anoriginal signal (original sample) per block split by splitter 102. Inother words, subtractor 104 calculates prediction errors (also referredto as residuals) of a block to be encoded (hereinafter referred to as acurrent block). Subtractor 104 then outputs the calculated predictionerrors to transformer 106.

The original signal is a signal input into encoder 100, and is a signalrepresenting an image for each picture included in a moving picture (forexample, a luma signal and two chroma signals). Hereinafter, a signalrepresenting an image is also referred to as a sample.

[Transformer]

Transformer 106 transforms spatial domain prediction errors intofrequency domain transform coefficients, and outputs the transformcoefficients to quantizer 108. More specifically, transformer 106applies, for example, a predefined discrete cosine transform (DCT) ordiscrete sine transform (DST) to spatial domain prediction errors.

Note that transformer 106 may adaptively select a transform type fromamong a plurality of transform types, and transform prediction errorsinto transform coefficients by using a transform basis functioncorresponding to the selected transform type. This sort of transform isalso referred to as explicit multiple core transform (EMT) or adaptivemultiple transform (AMT).

The transform types include, for example, DCT-II, DCT-V, DCT-VIII,DST-I, and DST-VII. FIG. 3 is a chart indicating transform basisfunctions for each transform type. In FIG. 3, N indicates the number ofinput pixels. For example, selection of a transform type from among theplurality of transform types may depend on the prediction type (intraprediction and inter prediction), and may depend on intra predictionmode.

Information indicating whether to apply such EMT or AMT (referred to as,for example, an AMT flag) and information indicating the selectedtransform type is signalled at the CU level. Note that the signaling ofsuch information need not be performed at the CU level, and may beperformed at another level (for example, at the sequence level, picturelevel, slice level, tile level, or CTU level).

Moreover, transformer 106 may apply a secondary transform to thetransform coefficients (transform result). Such a secondary transform isalso referred to as adaptive secondary transform (AST) or non-separablesecondary transform (NSST). For example, transformer 106 applies asecondary transform to each sub-block (for example, each 4×4 sub-block)included in the block of the transform coefficients corresponding to theintra prediction errors. Information indicating whether to apply NSSTand information related to the transform matrix used in NSST aresignalled at the CU level. Note that the signaling of such informationneed not be performed at the CU level, and may be performed at anotherlevel (for example, at the sequence level, picture level, slice level,tile level, or CTU level).

Here, a separable transform is a method in which a transform isperformed a plurality of times by separately performing a transform foreach direction according to the number of dimensions input. Anon-separable transform is a method of performing a collective transformin which two or more dimensions in a multidimensional input arecollectively regarded as a single dimension.

In one example of a non-separable transform, when the input is a 4×4block, the 4×4 block is regarded as a single array including 16components, and the transform applies a 16×16 transform matrix to thearray.

Moreover, similar to above, after an input 4×4 block is regarded as asingle array including 16 components, a transform that performs aplurality of Givens rotations on the array (i.e., a Hypercube-GivensTransform) is also one example of a non-separable transform.

[Quantizer]

Quantizer 108 quantizes the transform coefficients output fromtransformer 106. More specifically, quantizer 108 scans, in apredetermined scanning order, the transform coefficients of the currentblock, and quantizes the scanned transform coefficients based onquantization parameters (QP) corresponding to the transformcoefficients. Quantizer 108 then outputs the quantized transformcoefficients (hereinafter referred to as quantized coefficients) of thecurrent block to entropy encoder 110 and inverse quantizer 112.

A predetermined order is an order for quantizing/inverse quantizingtransform coefficients. For example, a predetermined scanning order isdefined as ascending order of frequency (from low to high frequency) ordescending order of frequency (from high to low frequency).

A quantization parameter is a parameter defining a quantization stepsize (quantization width). For example, if the value of the quantizationparameter increases, the quantization step size also increases. In otherwords, if the value of the quantization parameter increases, thequantization error increases.

[Entropy Encoder]

Entropy encoder 110 generates an encoded signal (encoded bitstream) byvariable length encoding quantized coefficients, which are inputs fromquantizer 108. More specifically, entropy encoder 110, for example,binarizes quantized coefficients and arithmetic encodes the binarysignal.

[Inverse Quantizer]

Inverse quantizer 112 inverse quantizes quantized coefficients, whichare inputs from quantizer 108. More specifically, inverse quantizer 112inverse quantizes, in a predetermined scanning order, quantizedcoefficients of the current block. Inverse quantizer 112 then outputsthe inverse quantized transform coefficients of the current block toinverse transformer 114.

[Inverse Transformer]

Inverse transformer 114 restores prediction errors by inversetransforming transform coefficients, which are inputs from inversequantizer 112. More specifically, inverse transformer 114 restores theprediction errors of the current block by applying an inverse transformcorresponding to the transform applied by transformer 106 on thetransform coefficients. Inverse transformer 114 then outputs therestored prediction errors to adder 116.

Note that since information is lost in quantization, the restoredprediction errors do not match the prediction errors calculated bysubtractor 104. In other words, the restored prediction errors includequantization errors.

[Adder]

Adder 116 reconstructs the current block by summing prediction errors,which are inputs from inverse transformer 114, and prediction samples,which are inputs from prediction controller 128. Adder 116 then outputsthe reconstructed block to block memory 118 and loop filter 120. Areconstructed block is also referred to as a local decoded block.

[Block Memory]

Block memory 118 is storage for storing blocks in a picture to beencoded (hereinafter referred to as a current picture) for reference inintra prediction. More specifically, block memory 118 storesreconstructed blocks output from adder 116.

[Loop Filter]

Loop filter 120 applies a loop filter to blocks reconstructed by adder116, and outputs the filtered reconstructed blocks to frame memory 122.A loop filter is a filter used in an encoding loop (in-loop filter), andincludes, for example, a deblocking filter (DF), a sample adaptiveoffset (SAO), and an adaptive loop filter (ALF).

In ALF, a least square error filter for removing compression artifactsis applied. For example, one filter from among a plurality of filters isselected for each 2×2 sub-block in the current block based on directionand activity of local gradients, and is applied.

More specifically, first, each sub-block (for example, each 2×2sub-block) is categorized into one out of a plurality of classes (forexample, 15 or 25 classes). The classification of the sub-block is basedon gradient directionality and activity. For example, classificationindex C is derived based on gradient directionality D (for example, 0 to2 or 0 to 4) and gradient activity A (for example, 0 to 4) (for example,C=5D+A). Then, based on classification index C, each sub-block iscategorized into one out of a plurality of classes (for example, 15 or25 classes).

For example, gradient directionality D is calculated by comparinggradients of a plurality of directions (for example, the horizontal,vertical, and two diagonal directions). Moreover, for example, gradientactivity A is calculated by summing gradients of a plurality ofdirections and quantizing the sum.

The filter to be used for each sub-block is determined from among theplurality of filters based on the result of such categorization.

The filter shape to be used in ALF is, for example, a circular symmetricfilter shape. FIG. 4A through FIG. 4C illustrate examples of filtershapes used in ALF. FIG. 4A illustrates a 5×5 diamond shape filter, FIG.4B illustrates a 7×7 diamond shape filter, and FIG. 4C illustrates a 9×9diamond shape filter. Information indicating the filter shape issignalled at the picture level. Note that the signaling of informationindicating the filter shape need not be performed at the picture level,and may be performed at another level (for example, at the sequencelevel, slice level, tile level, CTU level, or CU level).

The enabling or disabling of ALF is determined at the picture level orCU level. For example, for luma, the decision to apply ALF or not isdone at the CU level, and for chroma, the decision to apply ALF or notis done at the picture level. Information indicating whether ALF isenabled or disabled is signalled at the picture level or CU level. Notethat the signaling of information indicating whether ALF is enabled ordisabled need not be performed at the picture level or CU level, and maybe performed at another level (for example, at the sequence level, slicelevel, tile level, or CTU level).

The coefficients set for the plurality of selectable filters (forexample, 15 or 25 filters) is signalled at the picture level. Note thatthe signaling of the coefficients set need not be performed at thepicture level, and may be performed at another level (for example, atthe sequence level, slice level, tile level, CTU level, CU level, orsub-block level).

[Frame Memory]

Frame memory 122 is storage for storing reference pictures used in interprediction, and is also referred to as a frame buffer. Morespecifically, frame memory 122 stores reconstructed blocks filtered byloop filter 120.

[Intra Predictor]

Intra predictor 124 generates a prediction signal (intra predictionsignal) by intra predicting the current block with reference to a blockor blocks in the current picture and stored in block memory 118 (alsoreferred to as intra frame prediction). More specifically, intrapredictor 124 generates an intra prediction signal by intra predictionwith reference to samples (for example, luma and/or chroma values) of ablock or blocks neighboring the current block, and then outputs theintra prediction signal to prediction controller 128.

For example, intra predictor 124 performs intra prediction by using onemode from among a plurality of predefined intra prediction modes. Theintra prediction modes include one or more non-directional predictionmodes and a plurality of directional prediction modes.

The one or more non-directional prediction modes include, for example,planar prediction mode and DC prediction mode defined in theH.265/high-efficiency video coding (HEVC) standard (see NPTL 1).

The plurality of directional prediction modes include, for example, the33 directional prediction modes defined in the H.265/HEVC standard. Notethat the plurality of directional prediction modes may further include32 directional prediction modes in addition to the 33 directionalprediction modes (for a total of 65 directional prediction modes). FIG.5A illustrates 67 intra prediction modes used in intra prediction (twonon-directional prediction modes and 65 directional prediction modes).The solid arrows represent the 33 directions defined in the H.265/HEVCstandard, and the dashed arrows represent the additional 32 directions.

Note that a luma block may be referenced in chroma block intraprediction. In other words, a chroma component of the current block maybe predicted based on a luma component of the current block. Such intraprediction is also referred to as cross-component linear model (CCLM)prediction. Such a chroma block intra prediction mode that references aluma block (referred to as, for example, CCLM mode) may be added as oneof the chroma block intra prediction modes.

Intra predictor 124 may correct post-intra-prediction pixel values basedon horizontal/vertical reference pixel gradients. Intra predictionaccompanied by this sort of correcting is also referred to as positiondependent intra prediction combination (PDPC). Information indicatingwhether to apply PDPC or not (referred to as, for example, a PDPC flag)is, for example, signalled at the CU level. Note that the signaling ofthis information need not be performed at the CU level, and may beperformed at another level (for example, on the sequence level, picturelevel, slice level, tile level, or CTU level).

[Inter Predictor]

Inter predictor 126 generates a prediction signal (inter predictionsignal) by inter predicting the current block with reference to a blockor blocks in a reference picture, which is different from the currentpicture and is stored in frame memory 122 (also referred to as interframe prediction). Inter prediction is performed per current block orper sub-block (for example, per 4×4 block) in the current block. Forexample, inter predictor 126 performs motion estimation in a referencepicture for the current block or sub-block. Inter predictor 126 thengenerates an inter prediction signal of the current block or sub-blockby motion compensation by using motion information (for example, amotion vector) obtained from motion estimation. Inter predictor 126 thenoutputs the generated inter prediction signal to prediction controller128.

The motion information used in motion compensation is signalled. Amotion vector predictor may be used for the signaling of the motionvector. In other words, the difference between the motion vector and themotion vector predictor may be signalled.

Note that the inter prediction signal may be generated using motioninformation for a neighboring block in addition to motion informationfor the current block obtained from motion estimation. Morespecifically, the inter prediction signal may be generated per sub-blockin the current block by calculating a weighted sum of a predictionsignal based on motion information obtained from motion estimation and aprediction signal based on motion information for a neighboring block.Such inter prediction (motion compensation) is also referred to asoverlapped block motion compensation (OBMC).

In such an OBMC mode, information indicating sub-block size for OBMC(referred to as, for example, OBMC block size) is signalled at thesequence level. Moreover, information indicating whether to apply theOBMC mode or not (referred to as, for example, an OBMC flag) issignalled at the CU level. Note that the signaling of such informationneed not be performed at the sequence level and CU level, and may beperformed at another level (for example, at the picture level, slicelevel, tile level, CTU level, or sub-block level).

Hereinafter, the OBMC mode will be described in further detail. FIG. 5Bis a flowchart and FIG. 5C is a conceptual diagram for illustrating anoutline of a prediction image correction process performed via OBMCprocessing.

First, a prediction image (Pred) is obtained through typical motioncompensation using a motion vector (MV) assigned to the current block.

Next, a prediction image (Pred_L) is obtained by applying a motionvector (MV_L) of the encoded neighboring left block to the currentblock, and a first pass of the correction of the prediction image ismade by superimposing the prediction image and Pred_L.

Similarly, a prediction image (Pred_U) is obtained by applying a motionvector (MV_U) of the encoded neighboring upper block to the currentblock, and a second pass of the correction of the prediction image ismade by superimposing the prediction image resulting from the first passand Pred_U. The result of the second pass is the final prediction image.

Note that the above example is of a two-pass correction method using theneighboring left and upper blocks, but the method may be a three-pass orhigher correction method that also uses the neighboring right and/orlower block.

Note that the region subject to superimposition may be the entire pixelregion of the block, and, alternatively, may be a partial block boundaryregion.

Note that here, the prediction image correction process is described asbeing based on a single reference picture, but the same applies when aprediction image is corrected based on a plurality of referencepictures. In such a case, after corrected prediction images resultingfrom performing correction based on each of the reference pictures areobtained, the obtained corrected prediction images are furthersuperimposed to obtain the final prediction image.

Note that the unit of the current block may be a prediction block and,alternatively, may be a sub-block obtained by further dividing theprediction block.

One example of a method for determining whether to implement OBMCprocessing is by using an obmc_flag, which is a signal that indicateswhether to implement OBMC processing. As one specific example, theencoder determines whether the current block belongs to a regionincluding complicated motion. The encoder sets the obmc_flag to a valueof “1” when the block belongs to a region including complicated motionand implements OBMC processing when encoding, and sets the obmc_flag toa value of “0” when the block does not belong to a region includingcomplication motion and encodes without implementing OBMC processing.The decoder switches between implementing OBMC processing or not bydecoding the obmc_flag written in the stream and performing the decodingin accordance with the flag value.

Note that the motion information may be derived on the decoder sidewithout being signalled. For example, a merge mode defined in theH.265/HEVC standard may be used. Moreover, for example, the motioninformation may be derived by performing motion estimation on thedecoder side. In this case, motion estimation is performed without usingthe pixel values of the current block.

Here, a mode for performing motion estimation on the decoder side willbe described. A mode for performing motion estimation on the decoderside is also referred to as pattern matched motion vector derivation(PMMVD) mode or frame rate up-conversion (FRUC) mode.

One example of FRUC processing is illustrated in FIG. 5D. First, acandidate list (a candidate list may be a merge list) of candidates eachincluding a motion vector predictor is generated with reference tomotion vectors of encoded blocks that spatially or temporally neighborthe current block. Next, the best candidate MV is selected from among aplurality of candidate MVs registered in the candidate list. Forexample, evaluation values for the candidates included in the candidatelist are calculated and one candidate is selected based on thecalculated evaluation values.

Next, a motion vector for the current block is derived from the motionvector of the selected candidate. More specifically, for example, themotion vector for the current block is calculated as the motion vectorof the selected candidate (best candidate MV), as-is. Alternatively, themotion vector for the current block may be derived by pattern matchingperformed in the vicinity of a position in a reference picturecorresponding to the motion vector of the selected candidate. In otherwords, when the vicinity of the best candidate MV is searched via thesame method and an MV having a better evaluation value is found, thebest candidate MV may be updated to the MV having the better evaluationvalue, and the MV having the better evaluation value may be used as thefinal MV for the current block. Note that a configuration in which thisprocessing is not implemented is also acceptable.

The same processes may be performed in cases in which the processing isperformed in units of sub-blocks.

Note that an evaluation value is calculated by calculating thedifference in the reconstructed image by pattern matching performedbetween a region in a reference picture corresponding to a motion vectorand a predetermined region. Note that the evaluation value may becalculated by using some other information in addition to thedifference.

The pattern matching used is either first pattern matching or secondpattern matching. First pattern matching and second pattern matching arealso referred to as bilateral matching and template matching,respectively.

In the first pattern matching, pattern matching is performed between twoblocks along the motion trajectory of the current block in two differentreference pictures. Therefore, in the first pattern matching, a regionin another reference picture conforming to the motion trajectory of thecurrent block is used as the predetermined region for theabove-described calculation of the candidate evaluation value.

FIG. 6 is for illustrating one example of pattern matching (bilateralmatching) between two blocks along a motion trajectory. As illustratedin FIG. 6, in the first pattern matching, two motion vectors (MV0, MV1)are derived by finding the best match between two blocks along themotion trajectory of the current block (Cur block) in two differentreference pictures (Ref0, Ref1). More specifically, a difference between(i) a reconstructed image in a specified position in a first encodedreference picture (Ref0) specified by a candidate MV and (ii) areconstructed picture in a specified position in a second encodedreference picture (Ref1) specified by a symmetrical MV scaled at adisplay time interval of the candidate MV may be derived, and theevaluation value for the current block may be calculated by using thederived difference. The candidate MV having the best evaluation valueamong the plurality of candidate MVs may be selected as the final MV.

Under the assumption of continuous motion trajectory, the motion vectors(MV0, MV1) pointing to the two reference blocks shall be proportional tothe temporal distances (TD0, TD1) between the current picture (Cur Pic)and the two reference pictures (Ref0, Ref1). For example, when thecurrent picture is temporally between the two reference pictures and thetemporal distance from the current picture to the two reference picturesis the same, the first pattern matching derives a mirror basedbi-directional motion vector.

In the second pattern matching, pattern matching is performed between atemplate in the current picture (blocks neighboring the current block inthe current picture (for example, the top and/or left neighboringblocks)) and a block in a reference picture. Therefore, in the secondpattern matching, a block neighboring the current block in the currentpicture is used as the predetermined region for the above-describedcalculation of the candidate evaluation value.

FIG. 7 is for illustrating one example of pattern matching (templatematching) between a template in the current picture and a block in areference picture. As illustrated in FIG. 7, in the second patternmatching, a motion vector of the current block is derived by searching areference picture (Ref0) to find the block that best matches neighboringblocks of the current block (Cur block) in the current picture (CurPic). More specifically a difference between (i) a reconstructed imageof an encoded region that is both or one of the neighboring left andneighboring upper region and (ii) a reconstructed picture in the sameposition in an encoded reference picture (Ref0) specified by a candidateMV may be derived, and the evaluation value for the current block may becalculated by using the derived difference. The candidate MV having thebest evaluation value among the plurality of candidate MVs may beselected as the best candidate MV.

Information indicating whether to apply the FRUC mode or not (referredto as, for example, a FRUC flag) is signalled at the CU level. Moreover,when the FRUC mode is applied (for example, when the FRUC flag is set totrue), information indicating the pattern matching method (first patternmatching or second pattern matching) is signalled at the CU level. Notethat the signaling of such information need not be performed at the CUlevel, and may be performed at another level (for example, at thesequence level, picture level, slice level, tile level, CTU level, orsub-block level).

Here, a mode for deriving a motion vector based on a model assuminguniform linear motion will be described. This mode is also referred toas a bi-directional optical flow (BIO) mode.

FIG. 8 is for illustrating a model assuming uniform linear motion. InFIG. 8, (v_(x), v_(y)) denotes a velocity vector, and τ₀ and τ₁ denotetemporal distances between the current picture (Cur Pic) and tworeference pictures (Ref₀, Ref₁). (MVx₀, MVy₀) denotes a motion vectorcorresponding to reference picture Ref₀, and (MVx₁, MVy₁) denotes amotion vector corresponding to reference picture Ref₁.

Here, under the assumption of uniform linear motion exhibited byvelocity vector (v_(x), v_(y)), (MVx₀, MVy₀) and (MVx₁, MVy₁) arerepresented as (v_(x)τ₀, v_(y)τ₀) and (−v_(x)τ₁, −v_(y)τ₁),respectively, and the following optical flow equation is given.MATH. 1∂I ^((k)) /∂t+v _(x) ∂I ^((k)) /∂x+v _(y) ∂I ^((k)) /∂y=0.  (1)

Here, I^((k)) denotes a luma value from reference picture k (k=0, 1)after motion compensation. This optical flow equation shows that the sumof (i) the time derivative of the luma value, (ii) the product of thehorizontal velocity and the horizontal component of the spatial gradientof a reference picture, and (iii) the product of the vertical velocityand the vertical component of the spatial gradient of a referencepicture is equal to zero. A motion vector of each block obtained from,for example, a merge list is corrected pixel by pixel based on acombination of the optical flow equation and Hermite interpolation.

Note that a motion vector may be derived on the decoder side using amethod other than deriving a motion vector based on a model assuminguniform linear motion. For example, a motion vector may be derived foreach sub-block based on motion vectors of neighboring blocks.

Here, a mode in which a motion vector is derived for each sub-blockbased on motion vectors of neighboring blocks will be described. Thismode is also referred to as affine motion compensation prediction mode.

FIG. 9A is for illustrating deriving a motion vector of each sub-blockbased on motion vectors of neighboring blocks. In FIG. 9A, the currentblock includes 16 4×4 sub-blocks. Here, motion vector v₀ of the top leftcorner control point in the current block is derived based on motionvectors of neighboring sub-blocks, and motion vector v₁ of the top rightcorner control point in the current block is derived based on motionvectors of neighboring blocks. Then, using the two motion vectors v₀ andv₁, the motion vector (v_(x), v_(y)) of each sub-block in the currentblock is derived using Equation 2 below.

$\begin{matrix}{{Math}.\mspace{14mu} 2} & \; \\\left\{ \begin{matrix}{v_{x} = {{\frac{\left( {v_{1x} - v_{0x}} \right)}{w}x} - {\frac{\left( {v_{1y} - v_{0y}} \right)}{w}y} + v_{0x}}} \\{v_{y} = {{\frac{\left( {v_{1y} - v_{0y}} \right)}{w}x} + {\frac{\left( {v_{1x} - v_{0x}} \right)}{w}y} + v_{0y}}}\end{matrix} \right. & (2)\end{matrix}$

Here, x and y are the horizontal and vertical positions of thesub-block, respectively, and w is a predetermined weighted coefficient.

Such an affine motion compensation prediction mode may include a numberof modes of different methods of deriving the motion vectors of the topleft and top right corner control points. Information indicating such anaffine motion compensation prediction mode (referred to as, for example,an affine flag) is signalled at the CU level. Note that the signaling ofinformation indicating the affine motion compensation prediction modeneed not be performed at the CU level, and may be performed at anotherlevel (for example, at the sequence level, picture level, slice level,tile level, CTU level, or sub-block level).

[Prediction Controller]

Prediction controller 128 selects either the intra prediction signal orthe inter prediction signal, and outputs the selected prediction signalto subtractor 104 and adder 116.

Here, an example of deriving a motion vector via merge mode in a currentpicture will be given. FIG. 9B is for illustrating an outline of aprocess for deriving a motion vector via merge mode.

First, an MV predictor list in which candidate MV predictors areregistered is generated. Examples of candidate MV predictors include:spatially neighboring MV predictors, which are MVs of encoded blockspositioned in the spatial vicinity of the current block; a temporallyneighboring MV predictor, which is an MV of a block in an encodedreference picture that neighbors a block in the same location as thecurrent block; a combined MV predictor, which is an MV generated bycombining the MV values of the spatially neighboring MV predictor andthe temporally neighboring MV predictor; and a zero MV predictor, whichis an MV whose value is zero.

Next, the MV of the current block is determined by selecting one MVpredictor from among the plurality of IV predictors registered in the MVpredictor list.

Furthermore, in the variable-length encoder, a merge_idx, which is asignal indicating which MV predictor is selected, is written and encodedinto the stream.

Note that the MV predictors registered in the MV predictor listillustrated in FIG. 9B constitute one example. The number of MVpredictors registered in the MV predictor list may be different from thenumber illustrated in FIG. 9B, the MV predictors registered in the MVpredictor list may omit one or more of the types of MV predictors givenin the example in FIG. 9B, and the MV predictors registered in the MVpredictor list may include one or more types of MV predictors inaddition to and different from the types given in the example in FIG.9B.

Note that the final MV may be determined by performing DMVR processing(to be described later) by using the MV of the current block derived viamerge mode.

Here, an example of determining an MV by using DMVR processing will begiven.

FIG. 9C is a conceptual diagram for illustrating an outline of DMVRprocessing.

First, the most appropriate MVP set for the current block is consideredto be the candidate MV, reference pixels are obtained from a firstreference picture, which is a picture processed in the L0 direction inaccordance with the candidate MV, and a second reference picture, whichis a picture processed in the L1 direction in accordance with thecandidate MV, and a template is generated by calculating the average ofthe reference pixels.

Next, using the template, the surrounding regions of the candidate MVsof the first and second reference pictures are searched, and the MV withthe lowest cost is determined to be the final MV. Note that the costvalue is calculated using, for example, the difference between eachpixel value in the template and each pixel value in the regionssearched, as well as the MV value.

Note that the outlines of the processes described here are fundamentallythe same in both the encoder and the decoder.

Note that processing other than the processing exactly as describedabove may be used, so long as the processing is capable of deriving thefinal MV by searching the surroundings of the candidate MV.

Here, an example of a mode that generates a prediction image by usingLIC processing will be given.

FIG. 9D is for illustrating an outline of a prediction image generationmethod using a luminance correction process performed via LICprocessing.

First, an MV is extracted for obtaining, from an encoded referencepicture, a reference image corresponding to the current block.

Next, information indicating how the luminance value changed between thereference picture and the current picture is extracted and a luminancecorrection parameter is calculated by using the luminance pixel valuesfor the encoded left neighboring reference region and the encoded upperneighboring reference region, and the luminance pixel value in the samelocation in the reference picture specified by the MV.

The prediction image for the current block is generated by performing aluminance correction process by using the luminance correction parameteron the reference image in the reference picture specified by the MV.

Note that the shape of the surrounding reference region illustrated inFIG. 9D is just one example; the surrounding reference region may have adifferent shape.

Moreover, although a prediction image is generated from a singlereference picture in this example, in cases in which a prediction imageis generated from a plurality of reference pictures as well, theprediction image is generated after performing a luminance correctionprocess, via the same method, on the reference images obtained from thereference pictures.

One example of a method for determining whether to implement LICprocessing is by using an lic_flag, which is a signal that indicateswhether to implement LIC processing. As one specific example, theencoder determines whether the current block belongs to a region ofluminance change. The encoder sets the lic_flag to a value of “1” whenthe block belongs to a region of luminance change and implements LICprocessing when encoding, and sets the lic_flag to a value of “0” whenthe block does not belong to a region of luminance change and encodeswithout implementing LIC processing. The decoder switches betweenimplementing LIC processing or not by decoding the lic_flag written inthe stream and performing the decoding in accordance with the flagvalue.

One example of a different method of determining whether to implementLIC processing is determining so in accordance with whether LICprocessing was determined to be implemented for a surrounding block. Inone specific example, when merge mode is used on the current block,whether LIC processing was applied in the encoding of the surroundingencoded block selected upon deriving the MV in the merge mode processingmay be determined, and whether to implement LIC processing or not can beswitched based on the result of the determination. Note that in thisexample, the same applies to the processing performed on the decoderside.

[Decoder Outline]

Next, a decoder capable of decoding an encoded signal (encodedbitstream) output from encoder 100 will be described. FIG. 10 is a blockdiagram illustrating a functional configuration of decoder 200 accordingto Embodiment 1. Decoder 200 is a moving picture/picture decoder thatdecodes a moving picture/picture block by block.

As illustrated in FIG. 10, decoder 200 includes entropy decoder 202,inverse quantizer 204, inverse transformer 206, adder 208, block memory210, loop filter 212, frame memory 214, intra predictor 216, interpredictor 218, and prediction controller 220.

Decoder 200 is realized as, for example, a generic processor and memory.In this case, when a software program stored in the memory is executedby the processor, the processor functions as entropy decoder 202,inverse quantizer 204, inverse transformer 206, adder 208, loop filter212, intra predictor 216, inter predictor 218, and prediction controller220. Alternatively, decoder 200 may be realized as one or more dedicatedelectronic circuits corresponding to entropy decoder 202, inversequantizer 204, inverse transformer 206, adder 208, loop filter 212,intra predictor 216, inter predictor 218, and prediction controller 220.

Hereinafter, each component included in decoder 200 will be described.

[Entropy Decoder]

Entropy decoder 202 entropy decodes an encoded bitstream. Morespecifically for example, entropy decoder 202 arithmetic decodes anencoded bitstream into a binary signal. Entropy decoder 202 thendebinarizes the binary signal. With this, entropy decoder 202 outputsquantized coefficients of each block to inverse quantizer 204.

[Inverse Quantizer]

Inverse quantizer 204 inverse quantizes quantized coefficients of ablock to be decoded (hereinafter referred to as a current block), whichare inputs from entropy decoder 202. More specifically inverse quantizer204 inverse quantizes quantized coefficients of the current block basedon quantization parameters corresponding to the quantized coefficients.Inverse quantizer 204 then outputs the inverse quantized coefficients(i.e., transform coefficients) of the current block to inversetransformer 206.

[Inverse Transformer]

Inverse transformer 206 restores prediction errors by inversetransforming transform coefficients, which are inputs from inversequantizer 204.

For example, when information parsed from an encoded bitstream indicatesapplication of EMT or AMT (for example, when the AMT flag is set totrue), inverse transformer 206 inverse transforms the transformcoefficients of the current block based on information indicating theparsed transform type.

Moreover, for example, when information parsed from an encoded bitstreamindicates application of NSST, inverse transformer 206 applies asecondary inverse transform to the transform coefficients.

[Adder]

Adder 208 reconstructs the current block by summing prediction errors,which are inputs from inverse transformer 206, and prediction samples,which is an input from prediction controller 220. Adder 208 then outputsthe reconstructed block to block memory 210 and loop filter 212.

[Block Memory]

Block memory 210 is storage for storing blocks in a picture to bedecoded (hereinafter referred to as a current picture) for reference inintra prediction. More specifically, block memory 210 storesreconstructed blocks output from adder 208.

[Loop Filter]

Loop filter 212 applies a loop filter to blocks reconstructed by adder208, and outputs the filtered reconstructed blocks to frame memory 214and, for example, a display device.

When information indicating the enabling or disabling of ALF parsed froman encoded bitstream indicates enabled, one filter from among aplurality of filters is selected based on direction and activity oflocal gradients, and the selected filter is applied to the reconstructedblock.

[Frame Memory]

Frame memory 214 is storage for storing reference pictures used in interprediction, and is also referred to as a frame buffer. Morespecifically, frame memory 214 stores reconstructed blocks filtered byloop filter 212.

[Intra Predictor]

Intra predictor 216 generates a prediction signal (intra predictionsignal) by intra prediction with reference to a block or blocks in thecurrent picture and stored in block memory 210. More specifically, intrapredictor 216 generates an intra prediction signal by intra predictionwith reference to samples (for example, luma and/or chroma values) of ablock or blocks neighboring the current block, and then outputs theintra prediction signal to prediction controller 220.

Note that when an intra prediction mode in which a chroma block is intrapredicted from a luma block is selected, intra predictor 216 may predictthe chroma component of the current block based on the luma component ofthe current block.

Moreover, when information indicating the application of PDPC is parsedfrom an encoded bitstream, intra predictor 216 correctspost-intra-prediction pixel values based on horizontal/verticalreference pixel gradients.

[Inter Predictor]

Inter predictor 218 predicts the current block with reference to areference picture stored in frame memory 214. Inter prediction isperformed per current block or per sub-block (for example, per 4×4block) in the current block. For example, inter predictor 218 generatesan inter prediction signal of the current block or sub-block by motioncompensation by using motion information (for example, a motion vector)parsed from an encoded bitstream, and outputs the inter predictionsignal to prediction controller 220.

Note that when the information parsed from the encoded bitstreamindicates application of OBMC mode, inter predictor 218 generates theinter prediction signal using motion information for a neighboring blockin addition to motion information for the current block obtained frommotion estimation.

Moreover, when the information parsed from the encoded bitstreamindicates application of FRUC mode, inter predictor 218 derives motioninformation by performing motion estimation in accordance with thepattern matching method (bilateral matching or template matching) parsedfrom the encoded bitstream. Inter predictor 218 then performs motioncompensation using the derived motion information.

Moreover, when BIO mode is to be applied, inter predictor 218 derives amotion vector based on a model assuming uniform linear motion. Moreover,when the information parsed from the encoded bitstream indicates thataffine motion compensation prediction mode is to be applied, interpredictor 218 derives a motion vector of each sub-block based on motionvectors of neighboring blocks.

[Prediction Controller]

Prediction controller 220 selects either the intra prediction signal orthe inter prediction signal, and outputs the selected prediction signalto adder 208.

[Details of Inter Prediction]

In the inter prediction according to this embodiment, a motion vectorcandidate list is generated for a current partition to be processed, anda motion vector for the current partition is selected from the motionvector candidate list. A predicted image for the current partition isthen generated using the motion vector for the current partition. Thecurrent partition is then encoded and decoded using the predicted image.

Here, the partition is a partition included in an image, and can also berepresented as a block, an area, or a range. The partition may be acoding unit or a sub-coding unit obtainable by splitting a coding unit.In addition, the partition may be a prediction unit or a sub-predictionunit obtainable by splitting a prediction unit. In addition, thepartition may be a transform unit or a sub-transform unit obtainable bysplitting a transform unit.

In addition, the partition may be a rectangular partition or anon-rectangular partition. In addition, the rectangular partition may bea square partition or a non-square partition. In addition, thenon-rectangular partition may be a triangular partition or a partitionhaving another shape.

The motion vector candidate list can be represented as a motion vectorcandidate list or simply as a list. The motion vector candidate list forthe current partition includes a plurality of candidates for the motionvector for the current partition. The candidates can also be representedas motion vector predictors or motion vector candidates. The candidatesincluded in the motion vector candidate list for the current partitionare derived from, for example, motion vectors for neighboring partitionsthat neighbor the current partition. The motion vector candidate listmay be the merge list or the list in FRUC mode described above, or alist in another mode.

Specifically, motion vectors of neighboring partitions may be derived ascandidates. In addition, the candidates may be derived by scaling motionvectors of neighboring partitions. Here, the motion vectors of theneighboring partitions are motion vectors used to encode or decode theneighboring partitions.

In addition, among the plurality of candidates in the motion vectorcandidate list for the current partition, a merge index parameterindicating the motion vector for the current partition is encoded anddecoded. In this way, the same motion vector is selected and used forencoding and decoding in encoder 100 and decoder 200. The merge indexparameter can also be represented as a merge vector index parameter orsimply as an index. The merge index parameter indicates any of theplurality of candidates in the motion vector candidate list. As a matterof course, the motion vector candidate list is not limited to the motionvector candidate list in merge mode.

Hereinafter, descriptions are given of a plurality of specific modes forinter prediction performed by encoder 100 and decoder 200.

[First Aspect of Inter Prediction]

In this embodiment, a maximum number of motion vector candidates in amotion vector candidate list, that is, a maximum list size of the motionvector candidate list is dependent adaptively on a partition size. Themaximum list size can also be represented as an upper limit size orsimply as a list size.

A merge index parameter for selecting a motion vector from the motionvector candidate list is encoded into a bitstream in encoder 100, andthe encoded merge index parameter is decoded from the bitstream indecoder 200. At that time, the merge index parameter is encoded usingarithmetic encoding and is decoded using arithmetic decoding.

The code size of the merge index parameter is dependent on the maximumnumber of motion vector candidates. In other words, the code amount ofthe merge index parameter is dependent on the maximum list size of themotion vector candidate list. When the maximum list size is a first listsize smaller than a second list size, a merge index parameter is encodedand decoded using a small number of bits compared with the case wherethe maximum list size is the second list size.

For example, when the maximum list size is small, at least one of theupper limit or the lower limit in the number of bits of a merge indexparameter is small compared with the case where the maximum list size islarge.

FIG. 11 is a flow chart indicating the first aspect of inter predictionperformed by encoder 100 illustrated in FIG. 1.

First, inter predictor 126 in encoder 100 derives a maximum number basedon the partition size of a current partition to be processed (S101). Themaximum number is a maximum size of motion vector candidates for themotion vector to be used to predict the current partition. Interpredictor 126 derives a different maximum number based on a partitionsize. For example, inter predictor 126 may drive a smaller maximumnumber for a larger partition than for a smaller partition. In otherwords, inter predictor 126 may drive a larger maximum number for thesmaller partition than for the larger partition.

Next, inter predictor 126 generates a plurality of motion vectorcandidates for the current partition until the number of motion vectorcandidates reaches the maximum number to generate a motion vectorcandidate list (S102). Inter predictor 126 then selects a motion vectorfor the current partition from the motion vector candidate list (S103).

Next, entropy encoder 110 of encoder 100 encodes a merge index parameterindicating the motion vector for the current partition among theplurality of motion vector candidates in the motion vector candidatelist. At that time, entropy encoder 110 encodes, into a bitstream, amerge index parameter based on the derived maximum number (S104).

For example, entropy encoder 110 binarizes the merge index parameterinto a plurality of bits, and encodes the plurality of bits usingarithmetic encoding. In the binarization method and the arithmeticencoding method, the merge index parameter can be represented as a smallnumber of bits when the derived maximum number is small compared withthe case where the derived maximum number is large.

Lastly, encoder 100 encodes the current partition using the selectedmotion vector (S105).

Specifically, inter predictor 126 generates a predicted image of thecurrent partition using the selected motion vector. Subtractor 104derives a difference image between the original image and the predictedimage of the current partition. Transformer 106 transforms thedifference image into a plurality of transform coefficients. Quantizer108 quantizes the plurality of transform coefficients. Entropy encoder110 then encodes the quantized plurality of transform coefficients intoa bitstream.

FIG. 12 is a flow chart indicating the first aspect of inter predictionperformed by decoder 200 illustrated in FIG. 10.

First, inter predictor 218 in decoder 200 derives a maximum number basedon the partition size of a current partition to be processed (S111). Themaximum number is a maximum size of motion vector candidates for themotion vector to be used to predict the current partition. Interpredictor 218 derives a different maximum number based on a partitionsize. For example, inter predictor 218 may drive a smaller maximumnumber for a larger partition than for a smaller partition.

Next, inter predictor 218 generates a plurality of motion vectorcandidates for the current partition until the number of motion vectorcandidates reaches the maximum number to generate a motion vectorcandidate list (S112). In addition, entropy decoder 202 in decoder 200decodes, from a bitstream, a merge index parameter based on the derivedmaximum number (S113). For example, entropy decoder 202 decodes themerge index parameter using arithmetic decoding.

This merge index parameter indicates the motion vector for the partitionamong the plurality of motion vector candidates in the motion vectorcandidate list. Inter predictor 218 selects a motion vector for thecurrent partition from the motion vector candidate list based on themerge index parameter (S114). In the binarization method and thearithmetic encoding method, the merge index parameter can be representedas a small number of bits when the derived maximum number is smallcompared with the case where the derived maximum number is large.

Lastly, decoder 200 decodes the current partition using the selectedmotion vector (S115).

Specifically, inter predictor 218 generates a predicted image of thecurrent partition using the selected motion vector. Entropy decoder 202decodes, from the bitstream, the quantized plurality of transformcoefficients. Inverse quantizer 204 inverse quantizes the quantizedplurality of transform coefficients. Inverse transformer 206 transformsthe plurality of transform coefficients into a difference image. Adder208 adds the difference image and the predicted image to reconstruct animage.

The motion vector candidate list includes a plurality of candidates forthe motion vector for the current partition. The numbers of motionvector candidates vary between two partitions having different partitionsizes. In other words, two maximum list sizes for the two motion vectorcandidate lists to be generated for the two partitions having thedifferent partition sizes vary.

FIG. 13 illustrates examples of the maximum numbers of motion vectorcandidates relating to partition sizes. In this example, when thepartition size of a first partition is larger than the partition size ofa second partition, the maximum number of motion vectors for the firstpartition is smaller than the maximum number of motion vectors for thesecond partition.

In this way, it is highly likely that encoder 100 and decoder 200 canselect an appropriate motion vector from among a large number of motionvector candidates for the small partition.

On the other hand, there is a possibility that no appropriate motionvector is included in the large number of motion vector candidates forthe large partition. Accordingly, encoder 100 and decoder 200 arecapable of contributing to reduction in code amount of the indexindicating the motion vector by using the motion vector candidate listhaving the small maximum list size for the large partition.

FIG. 14 illustrates other examples of the maximum numbers of motionvector candidates relating to partition sizes. In this example, when thepartition size of a first partition is larger than the partition size ofa second partition, the maximum number of motion vectors for the firstpartition is larger than the maximum number of motion vectors for thesecond partition. In other words, when the partition size of the firstpartition is smaller than the partition size of the second partition,the maximum number of motion vectors for the first partition is smallerthan the maximum number of motion vectors for the second partition.

When a small block is used, the total number of blocks increases. Inthis way, there is a possibility that the total number of blocksincreases and the code amount increases. In the examples in FIG. 14,encoder 100 and decoder 200 are capable of reducing increase in codeamount by using the motion vector candidate list having the smallmaximum list size for the small partition.

In this aspect, the maximum numbers of motion vector candidates for themotion vectors are adaptively determined based on the partition sizes.In this way, it is possible to increase the coding efficiency andoptimize the computation amount. In addition, it is possible to increasethe image quality through the appropriate prediction processing.

It is to be noted that encoder 100 and decoder 200 perform interprediction in the same manner. In addition, at least part of this aspectmay be combined with at least part of other one or more aspects. Inaddition, any of the processes, elements, syntaxes, features, and anoptional combination of these according to this aspect may be applied toany of the aspects.

All the above-described processes do not always need to be included in amethod, and all the elements do not always need to be included in adevice. In other words, part of the plurality of processes describedabove do not always need to be included in the method, and part of theplurality of elements described above do not always need to be includedin the device.

[Second Aspect of Inter Prediction]

In this embodiment, a maximum number of motion vector candidates in amotion vector candidate list, that is, a maximum list size of the motionvector candidate list is dependent adaptively on a partition shape. Themaximum list size can also be represented as an upper limit size orsimply as a list size.

A merge index parameter for selecting a motion vector from the motionvector candidate list is encoded into a bitstream in encoder 100, andthe encoded merge index parameter is decoded from the bitstream indecoder 200. At that time, the merge index parameter is encoded usingarithmetic encoding and is decoded using arithmetic decoding.

The code size of the merge index parameter is dependent on the maximumnumber of motion vector candidates. In other words, the code amount ofthe merge index parameter is dependent on the maximum list size of themotion vector candidate list. When the maximum list size is a first listsize smaller than a second list size, a merge index parameter is encodedand decoded using a small number of bits compared with the case wherethe maximum list size is the second list size.

For example, when the maximum list size is small, at least one of theupper limit or the lower limit in the number of bits of a merge indexparameter is small compared with the case where the maximum list size islarge.

FIG. 15 is a flow chart indicating the second aspect of inter predictionperformed by encoder 100 illustrated in FIG. 1.

First, inter predictor 126 in encoder 100 derives a maximum number basedon the partition shape of a current partition to be processed (S201).The maximum number is a maximum size of motion vector candidates for themotion vector to be used to predict the current partition. Interpredictor 126 derives a different maximum number based on a differentpartition shape. For example, inter predictor 126 may derive a smallermaximum number for a non-rectangular (triangular) partition than amaximum number for a rectangular partition.

Next, inter predictor 126 generates a plurality of motion vectorcandidates for the current partition until the number of motion vectorcandidates reaches the maximum number to generate a motion vectorcandidate list (S202). Inter predictor 126 then selects a motion vectorfor the current partition from the motion vector candidate list (S203).

Next, entropy encoder 110 of encoder 100 encodes a merge index parameterindicating the motion vector for the current partition among theplurality of motion vector candidates in the motion vector candidatelist. At that time, entropy encoder 110 encodes, into a bitstream, amerge index parameter based on the derived maximum number (S204).

For example, entropy encoder 110 binarizes the merge index parameterinto a plurality of bits, and encodes the plurality of bits usingarithmetic encoding. In the binarization method and the arithmeticencoding method, the merge index parameter can be represented as a smallnumber of bits when the derived maximum number is smaller than when thederived maximum number is large.

Lastly encoder 100 encodes the current partition using the selectedmotion vector (S205).

Specifically, inter predictor 126 generates a predicted image of thecurrent partition using the selected motion vector. Subtractor 104derives a difference image between the original image and the predictedimage of the current partition. Transformer 106 transforms thedifference image into a plurality of transform coefficients. Quantizer108 quantizes the plurality of transform coefficients. Entropy encoder110 then encodes the quantized plurality of transform coefficients intoa bitstream.

FIG. 16 is a flow chart indicating the second aspect of inter predictionperformed by decoder 200 illustrated in FIG. 10.

First, inter predictor 218 in decoder 200 derives a maximum number basedon the partition shape of a current partition to be processed (S211).The maximum number is a maximum size of motion vector candidates for themotion vector to be used to predict the current partition. Interpredictor 218 derives a different maximum number based on a differentpartition shape. For example, inter predictor 218 may derive a smallermaximum number for a non-rectangular (triangular) partition than amaximum number for a rectangular partition.

Next, inter predictor 218 generates a plurality of motion vectorcandidates for the current partition until the number of motion vectorcandidates reaches the maximum number to generate a motion vectorcandidate list (S212). In addition, entropy decoder 202 in decoder 200decodes, from a bitstream, a merge index parameter based on the derivedmaximum number (S213). For example, entropy decoder 202 decodes themerge index parameter using arithmetic decoding.

This merge index parameter indicates the motion vector for the partitionamong the plurality of motion vector candidates in the motion vectorcandidate list. Inter predictor 218 selects a motion vector for thecurrent partition from the motion vector candidate list based on themerge index parameter (S214). In the binarization method and thearithmetic encoding method, the merge index parameter can be representedas a small number of bits when the derived maximum number is smallcompared with the case where the derived maximum number is large.

Lastly, decoder 200 decodes the current partition using the selectedmotion vector (S215).

Specifically, inter predictor 218 generates a predicted image of thecurrent partition using the selected motion vector. Entropy decoder 202decodes, from the bitstream, the quantized plurality of transformcoefficients. Inverse quantizer 204 inverse quantizes the quantizedplurality of transform coefficients. Inverse transformer 206 transformsthe plurality of transform coefficients into a difference image. Adder208 adds the difference image and the predicted image to reconstruct animage.

The motion vector candidate list includes a plurality of candidates forthe motion vector for current partition. The numbers of maximum motionvector candidates vary between two partitions having different partitionshapes. In other words, two maximum list sizes for the two motion vectorcandidate lists to be generated for the two partitions having thedifferent partition shapes vary.

FIG. 17 illustrates examples of the maximum numbers of motion vectorcandidates relating to partition shapes. In these examples, the maximumnumber of motion vector candidates for a triangular partition is smallerthan the maximum number of motion vector candidates for a rectangularpartition.

In this way, it is highly likely that encoder 100 and decoder 200 canselect an appropriate motion vector from among a large number of motionvector candidates for the rectangular partition.

On the other hand, there is a possibility that the number of referableprocessed partitions is small and the number of derivable motion vectorcandidates is small around the triangular partition. Accordingly,encoder 100 and decoder 200 are capable of contributing to reduction incode amount of the index indicating the motion vector by using themotion vector candidate list having the small maximum list size for thetriangular partition.

However, for example, when a partition that neighbors the hypotenuse ofa triangular partition is available, there is a possibility that thenumber of referable processed partitions is large and that the number ofderivable motion vector candidates is large around the triangularpartition. Accordingly, the maximum number of motion vectors for thetriangular partition is not limited to the examples in FIG. 17, and maybe larger than the maximum number of motion vectors for the rectangularpartition.

FIG. 18 illustrates other examples of the maximum numbers of motionvector candidates relating to partition shapes. In these examples, themaximum number of motion vector candidates for the rectangular(non-square) partition is larger than the maximum number of motionvector candidates for the square partition.

In this way, encoder 100 and decoder 200 are capable of selecting anappropriate motion vector from among a large number of motion vectorcandidates for a partition having a complicated shape. On the otherhand, encoder 100 and decoder 200 are capable of simplifying processingby using a motion vector candidate list having a small maximum list sizefor a partition having a simple shape. In this way, encoder 100 anddecoder 200 are capable of contributing to reduction in code amount ofthe index indicating the motion vector.

In addition, for example, a rectangular (non-square) partition isassumed to have different characteristics between the long side and theshort side. Accordingly it is assumed to be effective that acomparatively large number of motion vector candidates is derived from aplurality of neighboring partitions, and that a motion vector isselected from the comparatively large number of motion vectorcandidates. On the other hand, a square partition is assumed not to havecharacteristics similar to the rectangular (non-square) partition. Thus,it is assumed to be effective that processing is simplified.

However, there is a possibility that no appropriate motion vector isincluded in the large number of motion vector candidates for acomplicated partition. Accordingly, it may be effective to reduce thecode amount of the index indicating the motion vector by using themotion vector candidate list having a small maximum list size for thecomplicated partition. Accordingly, the maximum number of motion vectorcandidates for a rectangular (non-square) partition is not limited tothe example in FIG. 18, and may be smaller than the maximum number ofmotion vectors for a square partition.

In this aspect, the maximum numbers of motion vector candidates for themotion vectors are adaptively determined based on the partition shapes.In this way, it is possible to increase the coding efficiency andoptimize the computation amount. In addition, it is possible to increasethe image quality through the appropriate prediction processing.

It is to be noted that encoder 100 and decoder 200 perform interprediction in the same manner. In addition, at least part of this aspectmay be combined with at least part of other one or more aspects. Inaddition, any of the processes, elements, syntaxes, features, and anoptional combination of these according to this aspect may be applied toany of the aspects.

All the above-described processes do not always need to be included in amethod, and all the elements do not always need to be included in adevice. In other words, part of the plurality of processes describedabove do not always need to be included in the method, and part of theplurality of elements described above do not always need to be includedin the device.

[Third Aspect of Inter Prediction]

In this embodiment, the order of motion vector candidates in a motionvector candidate list, that is, the order of candidates in the motionvector candidate list is dependent adaptively on a partition size. Aplurality of motion vector candidates may be derived in an initialorder, and may be re-arranged based on a partition size.

A merge index parameter for selecting a motion vector from the motionvector candidate list is encoded into a bitstream in encoder 100, andthe encoded merge index parameter is decoded from the bitstream indecoder 200. At that time, the merge index parameter is encoded usingarithmetic encoding and is decoded using arithmetic decoding.

The code size of the merge index parameter is dependent on the positionof the motion vector candidate indicating the merge index parameter inthe order of candidates in the motion vector candidate list. The mergeindex parameter indicating a motion vector candidate arranged beforeanother motion vector candidate in the order of candidates in the motionvector candidate list is encoded and decoded using a small number ofbits compared with the case of the merge index parameter indicating theother motion vector candidate arranged after.

FIG. 19 is a flow chart indicating the third aspect of inter predictionperformed by encoder 100 illustrated in FIG. 1.

First, inter predictor 126 in encoder 100 generates, for a partition, amotion vector candidate list including a plurality of motion vectorcandidates in order which is dependent on the partition size (S301). Forexample, inter predictor 126 may generate, for a large partition, amotion vector candidate list including a plurality of motion vectorcandidates in order different from the order in the case of a smallpartition.

Next, inter predictor 126 then selects a motion vector for the currentpartition from the motion vector candidate list (S302).

Next, entropy encoder 110 of encoder 100 encodes, into a bitstream, amerge index parameter indicating the motion vector for the currentpartition among the plurality of motion vector candidates in the motionvector candidate list (S303). For example, entropy encoder 110 binarizesthe merge index parameter into a plurality of bits, and encodes theplurality of bits using arithmetic encoding.

Lastly, encoder 100 encodes the current partition using the selectedmotion vector (S304).

Specifically, inter predictor 126 generates a predicted image of thecurrent partition using the selected motion vector. Subtractor 104derives a difference image between the original image and the predictedimage of the current partition. Transformer 106 transforms thedifference image into a plurality of transform coefficients. Quantizer108 quantizes the plurality of transform coefficients. Entropy encoder110 then encodes the quantized plurality of transform coefficients intoa bitstream.

FIG. 20 is a flow chart indicating the third aspect of inter predictionperformed by decoder 200 illustrated in FIG. 10.

First, inter predictor 218 in decoder 200 generates, for a partition, amotion vector candidate list including a plurality of motion vectorcandidates in order which is dependent on the partition size (S311). Forexample, inter predictor 218 may generate, for a large partition, amotion vector candidate list including a plurality of motion vectorcandidates in order which is different from the order in the case of asmall partition.

Next, entropy decoder 202 in decoder 200 decodes, from a bitstream, amerge index parameter indicating the motion vector for the currentpartition among the plurality of motion vector candidates in the motionvector candidate list (S312). For example, entropy decoder 202 decodesthe merge index parameter using arithmetic decoding.

Inter predictor 218 then selects a motion vector for the currentpartition from the motion vector candidate list based on the merge indexparameter (S313).

Lastly, decoder 200 decodes the current partition using the selectedmotion vector (S314).

Specifically, inter predictor 218 generates a predicted image of thecurrent partition using the selected motion vector. Entropy decoder 202decodes, from the bitstream, the quantized plurality of transformcoefficients. Inverse quantizer 204 inverse quantizes the quantizedplurality of transform coefficients. Inverse transformer 206 transformsthe plurality of transform coefficients into a difference image. Adder208 adds the difference image and the predicted image to reconstruct animage.

As described above, the motion vector candidate list generated for eachpartition includes the plurality of motion vector candidates for themotion vector for the partition. The orders of candidates vary betweenthe two motion vector candidate lists generated respectively for the twopartitions having different partition sizes.

FIG. 21 illustrates examples of the orders of candidates relating topartition sizes. In these examples, the orders of candidates varybetween a large partition and a small partition.

FIG. 22 illustrates other examples of the orders of candidates relatingto partition sizes. In these examples, the order of candidates varybetween an M×M/2 block and an M×M square block.

In this aspect, the orders of motion vector candidates for the motionvectors are adaptively determined based on the partition sizes. In thisway, it is possible to increase the coding efficiency.

It is to be noted that encoder 100 and decoder 200 perform interprediction in the same manner. In addition, at least part of this aspectmay be combined with at least part of other one or more aspects. Inaddition, any of the processes, elements, syntaxes, features, and anoptional combination of these according to this aspect may be applied toany of the aspects.

All the above-described processes do not always need to be included in amethod, and all the elements do not always need to be included in adevice. In other words, part of the plurality of processes describedabove do not always need to be included in the method, and part of theplurality of elements described above do not always need to be includedin the device.

[Fourth Aspect of Inter Prediction]

In this embodiment, the order of motion vector candidates in a motionvector candidate list, that is, the order of candidates in the motionvector candidate list is dependent adaptively on a partition shape. Aplurality of motion vector candidates may be derived in an initialorder, and may be re-arranged based on a partition shape.

A merge index parameter for selecting a motion vector from the motionvector candidate list is encoded into a bitstream in encoder 100, andthe encoded merge index parameter is decoded from the bitstream indecoder 200. At that time, the merge index parameter is encoded usingarithmetic encoding and is decoded using arithmetic decoding.

The code size of the merge index parameter is dependent on the positionof the motion vector candidate indicating the merge index parameter inthe order of candidates in the motion vector candidate list. The mergeindex parameter indicating a motion vector candidate arranged beforeanother motion vector candidate in the order of candidates in the motionvector candidate list is encoded and decoded using a small number ofbits compared with the case of the other merge index parameterindicating the other motion vector candidate arranged after.

FIG. 23 is a flow chart indicating the fourth aspect of inter predictionperformed by encoder 100 illustrated in FIG. 1.

First, inter predictor 126 in encoder 100 generates, for a partition, amotion vector candidate list including a plurality of motion vectorcandidates in order which is dependent on the partition shape (S401).For example, inter predictor 126 may generate, for a non-rectangular(triangular) partition, a motion vector candidate list including aplurality of motion vector candidates in order which is different fromthe order in the case of a rectangular partition.

Next, inter predictor 126 then selects a motion vector for the currentpartition from the motion vector candidate list (S402).

Next, entropy encoder 110 of encoder 100 encodes, into a bitstream, amerge index parameter indicating the motion vector for the currentpartition among the plurality of motion vector candidates in the motionvector candidate list (S403). For example, entropy encoder 110 binarizesthe merge index parameter into a plurality of bits, and encodes theplurality of bits using arithmetic encoding.

Lastly, encoder 100 encodes the current partition using the selectedmotion vector (S404).

Specifically, inter predictor 126 generates a predicted image of thecurrent partition using the selected motion vector. Subtractor 104derives a difference image between the original image and the predictedimage of the current partition. Transformer 106 transforms thedifference image into a plurality of transform coefficients. Quantizer108 quantizes the plurality of transform coefficients. Entropy encoder110 then encodes the quantized plurality of transform coefficients intoa bitstream.

FIG. 24 is a flow chart indicating the fourth aspect of inter predictionperformed by decoder 200 illustrated in FIG. 10.

First, inter predictor 218 in decoder 200 generates, for a currentpartition to be decoded, a motion vector candidate list including aplurality of motion vector candidates in order which is dependent on thepartition shape (S411). For example, inter predictor 218 may generate,for a non-rectangular (triangular) partition, a motion vector candidatelist including a plurality of motion vector candidates in order which isdifferent from the order in the case of a rectangular partition.

Next, entropy decoder 202 in decoder 200 decodes, from a bitstream, amerge index parameter indicating the motion vector for the currentpartition among the plurality of motion vector candidates in the motionvector candidate list (S412). For example, entropy decoder 202 decodesthe merge index parameter using arithmetic decoding.

Inter predictor 218 then selects a motion vector for the currentpartition from the motion vector candidate list based on the merge indexparameter (S413).

Lastly, decoder 200 decodes the current partition using the selectedmotion vector (S414).

Specifically, inter predictor 218 generates a predicted image of thecurrent partition using the selected motion vector. Entropy decoder 202decodes, from the bitstream, the quantized plurality of transformcoefficients. Inverse quantizer 204 inverse quantizes the quantizedplurality of transform coefficients. Inverse transformer 206 transformsthe plurality of transform coefficients into a difference image. Adder208 adds the difference image and the predicted image to reconstruct animage.

As described above, the motion vector candidate list generated for eachpartition includes the plurality of motion vector candidates for themotion vector for the partition. The orders of candidates vary betweenthe two motion vector candidate lists generated respectively for the twopartitions having different partition shapes.

FIG. 25 illustrates examples of the orders of candidates relating topartition shapes. In these examples, the orders of candidates varybetween a rectangular partition and a triangular partition.

FIG. 26 illustrates other examples of the orders of candidates relatingto partition shapes. In these examples, the orders of candidates varybetween an M×N block and an N×M block. These two partitions may have thesame shape and different orientations. When the orientations of thepartitions having the same shape are different, the orders of candidatesmay vary. In other words, the orders of candidates may be dependent onthe orientations of partition shapes. In other words, the orders ofcandidates may be dependent on the partition shapes which have anorientation as an attribute.

It is to be noted that FIG. 26 illustrates an example, and the orders ofcandidates may not be dependent on the orientations of partition shapes.In other words, the orders of candidates may be dependent on thepartition shapes which do not have orientations as attributes. Forexample, these two partitions may have different partition shapes orhave the same order of candidates when the partition shapes are thesame.

In this aspect, the orders of motion vector candidates for the motionvectors are adaptively determined based on the partition shapes. In thisway, it is possible to increase the coding efficiency.

It is to be noted that encoder 100 and decoder 200 perform interprediction in the same manner. In addition, at least part of this aspectmay be combined with at least part of other one or more aspects. Inaddition, any of the processes, elements, syntaxes, features, and anoptional combination of these according to this aspect may be applied toany of the aspects.

All the above-described processes do not always need to be included in amethod, and all the elements do not always need to be included in adevice. In other words, part of the plurality of processes describedabove do not always need to be included in the method, and part of theplurality of elements described above do not always need to be includedin the device.

[Mounting Example]

FIG. 27 is a block diagram illustrating an example of mounting encoder100. Encoder 100 includes circuitry 160 and memory 162. For example, aplurality of constituent elements of encoder 100 illustrated in FIG. 1are mounted on processor 160 and memory 162 illustrated in FIG. 27.

Circuitry 160 is an electronic circuit accessible to memory 162, andperforms information processing. For example, circuitry 160 is adedicated or general-purpose electronic circuitry which encodes videosusing memory 162. Circuitry 160 may be a processor such as a CPU.Circuitry 160 may be a combination of a plurality of electroniccircuits.

In addition, for example, circuitry 160 may take the roles ofconstituent elements other than the constituent elements for storinginformation among the plurality of constituent elements of encoder 100illustrated in FIG. 1. In other words, circuitry 160 may perform theabove-described operations by these constituent elements.

Memory 162 is general-purpose or dedicated memory in which informationfor allowing circuitry 160 to encode a video is stored. Memory 162 maybe electronic circuitry, may be connected to circuitry 160, and may beincluded in circuitry 160.

Memory 162 may be a combination of a plurality of electronic circuits,or may be configured with a plurality of sub-memories. Memory 162 may bea magnetic disc, an optical disc, or the like, or may be represented asstorage, a recording medium, or the like. Memory 162 may be non-volatilememory or volatile memory.

For example, memory 162 may take the roles of constituent elements forstoring information among the plurality of constituent elements ofencoder 100 illustrated in FIG. 1. Specifically, memory 162 may take theroles of block memory 118 and frame memory 122 illustrated in FIG. 1.

For example, a video to be encoded or a bitstream corresponding to theencoded video may be recorded onto memory 162. Memory 162 may include aprogram for causing circuitry 160 to encode a video recorded thereon.

In encoder 100, it is not always necessary that all the constituentelements illustrated in FIG. 1 be mounted, and that all theabove-described processes be performed. Part of the constituent elementsillustrated in FIG. 1 may be included in another device, and part of theabove-described processes may be executed by another device. Inaddition, in encoder 100, by means of the part of the plurality ofconstituent elements illustrated in FIG. 1 being mounted and the part ofthe processes described above being performed, information forprediction can be configured appropriately.

FIG. 28 is a flow chart indicating an example of an operation performedby encoder 100 illustrated in FIG. 27. For example, when encoder 100encodes a video into a bitstream using a predicted image, circuitry 160in encoder 100 performs the operation indicated in FIG. 28 using memory162.

First, circuitry 160 generates a list including a plurality ofcandidates for a first motion vector for a first partition in a video(S501). The plurality of candidates included in this list includes acandidate derived from a second motion vector for a second partitiondifferent from the first partition in the video. In addition, at leastone of the maximum list size of the list or the order of the pluralityof candidates included in the list is dependent on at least one of thepartition size or the partition shape of the first partition.

Next, circuitry 160 selects a motion vector from the plurality ofcandidates included in the list (S502). In addition, circuitry 160encodes, into a bitstream, an index indicating the first motion vectoramong the plurality of candidates included in the list based on themaximum list size (S503). Circuitry 160 then generates a predicted imageof the first partition using the first motion vector (S504).

In this way encoder 100 is capable of generating the motion vectorcandidate list based on the maximum list size or the order of candidateswhich is dependent on the partition size or the partition shape.Accordingly, encoder 100 is capable of generating an appropriatecandidate list based on the partition size or the partition shape. Inother words, encoder 100 is capable of appropriately configuringinformation for prediction. Accordingly, encoder 100 is capable ofcontributing to reduction in code amount.

For example, when the partition size is a first partition size, themaximum list size may be the first list size. When the partition size isa second partition size smaller than the first partition size, themaximum list size may be a second list size larger than the first listsize.

In this way, encoder 100 is capable of selecting an appropriate motionvector from among a large number of motion vector candidates for a smallpartition. On the other hand, there is a possibility that no appropriatemotion vector is included in the large number of motion vectorcandidates for the large partition. Accordingly, encoder 100 is capableof contributing to reduction in code amount of the index indicating themotion vector by using a motion vector candidate list having a smallmaximum list size for the large partition.

For example, when the partition size is a first partition size, themaximum list size may be the first list size. When the partition size isa second partition size smaller than the first partition size, themaximum list size may be a second list size smaller than the first listsize.

In this way, encoder 100 is capable of selecting the appropriate motionvector from among the large number of motion vector candidates for thelarge partition. Accordingly encoder 100 is capable of simplifying theprocessing and contributing to reduction in code amount of the indexindicating the motion vector by using the motion vector candidate listhaving the small maximum list size for the large partition.

In addition, for example, the maximum list size may be dependent on thepartition shape which is one of a square, a rectangle, or a triangle. Inthis way, encoder 100 is capable of generating an appropriate candidatelist based on the partition shape which is one of a square, a rectangle,or a triangle.

In addition, for example, when the partition shape is a triangle, themaximum list size may be the first list size. When the partition shapeis not a triangle, the maximum list size may be a second list sizelarger than the first list size.

In this way, encoder 100 is capable of selecting an appropriate motionvector from among a large number of motion vector candidates for arectangular partition. On the other hand, there is a possibility thatthe number of referable processed partitions is small and the number ofderivable motion vector candidates is small around the triangularpartition. Accordingly, encoder 100 is capable of contributing toreduction in code amount of the index indicating the motion vector byusing a motion vector candidate list having a small maximum list sizefor the triangular partition.

In addition, for example, when the partition shape is a square, themaximum list size may be the first list size. When the partition shapeis not a square, the maximum list size may be a second list size largerthan the first list size.

In this way, encoder 100 is capable of selecting an appropriate motionvector from among a large number of motion vector candidates for apartition having a complicated shape. Accordingly, encoder 100 iscapable of simplifying processing and contributing to reduction in codeamount of an index indicating a motion vector by using a motion vectorcandidate list having a small maximum list size for a partition having asimple shape.

In addition, for example, when the maximum list size is the first listsize, circuitry 160 may encode an index using a first number of bits.When the maximum list size is a second list size larger than the firstlist size, circuitry 160 may then encode an index using a second numberof bits larger than the first number of bits. In this way, encoder 100is capable of encoding the index using an appropriate number of bitsbased on the maximum list size.

In addition, for example, the second partition may be a partition thatneighbors the first partition.

In this way, encoder 100 is capable of deriving a candidate for themotion vector for the current partition from a motion vector of apartition that neighbors the current partition. Accordingly, encoder 100is capable of appropriately deriving the candidate for the motion vectorfor the current partition from the motion vector that is assumed to besimilar to the motion vector for the current partition.

FIG. 29 is a block diagram illustrating an example of mounting decoder200. Decoder 200 includes circuitry 260 and memory 262. For example, aplurality of constituent elements of decoder 200 illustrated in FIG. 10are mounted on circuitry 260 and memory 262 illustrated in FIG. 29.

Circuitry 260 is an electronic circuit accessible to memory 262, andperforms information processing. For example, circuitry 260 is adedicated or general-purpose electronic circuitry which decodes videosusing memory 262. Circuitry 260 may be a processor such as a CPU.Circuitry 260 may be a combination of a plurality of electroniccircuits.

In addition, for example, circuitry 260 may take the roles ofconstituent elements other than the constituent elements for storinginformation among the plurality of constituent elements of decoder 200illustrated in FIG. 10. In other words, circuitry 260 may perform theabove-described operations by these constituent elements.

Memory 262 is general-purpose or dedicated memory in which informationfor allowing circuitry 260 to decode a video is stored. Memory 262 maybe electronic circuitry, may be connected to circuitry 260, and may beincluded in circuitry 260.

Memory 262 may be a combination of a plurality of electronic circuits,or may be configured with a plurality of sub-memories. Memory 262 may bea magnetic disc, an optical disc, or the like, or may be represented asstorage, a recording medium, or the like. Memory 262 may be non-volatilememory or volatile memory.

For example, memory 262 may take the roles of constituent elements forstoring information among the plurality of constituent elements ofdecoder 200 illustrated in FIG. 10. Specifically, memory 262 may takesthe roles of block memory 210 and frame memory 214 illustrated in FIG.10.

For example, a bitstream corresponding to an encoded video or a decodedvideo may be recorded onto memory 262. Memory 262 may include a programfor causing circuitry 260 to decode a video recorded thereon.

In decoder 200, it is not always necessary that all the constituentelements illustrated in FIG. 10 be mounted, and that all theabove-described processes be performed. Part of the constituent elementsillustrated in FIG. 10 may be included in another device, and part ofthe above-described processes may be executed by another device. Inaddition, in decoder 200, by means of the part of the plurality ofconstituent elements illustrated in FIG. 10 being mounted and the partof the processes described above being performed, information forprediction can be configured appropriately.

FIG. 30 is a flow chart indicating an example of an operation performedby decoder 200 illustrated in FIG. 29. For example, when decoder 200decodes, from a bitstream, a video using a predicted image, circuitry260 in decoder 200 performs the operation indicated in FIG. 30 usingmemory 262.

First, circuitry 260 generates a list including a plurality ofcandidates for a first motion vector for a first partition in a video(S511). The plurality of candidates included in this list includescandidates derived from a second motion vector for a second partitiondifferent from the first partition in the video. In addition, at leastone of the maximum list size of the list or the order of the pluralityof candidates included in the list is dependent on at least one of thepartition size and the partition shape of the first partition.

In addition, circuitry 260 decodes, from a bitstream, an indexindicating the first motion vector among the plurality of candidatesincluded in the list based on the maximum list size (S512). Next,circuitry 260 selects a first motion vector from the plurality ofcandidates included in the list using the index (S513). Circuitry 260then generates a predicted image of the first partition using the firstmotion vector (S14).

In this way decoder 200 is capable of generating a motion vectorcandidate list based on the maximum list size or the order of candidateswhich is dependent on the partition size or the partition shape.Accordingly, decoder 200 is capable of generating an appropriatecandidate list based on the partition size or the partition shape. Inother words, decoder 200 is capable of appropriately configuringinformation for prediction. Accordingly, decoder 200 is capable ofcontributing to reduction in code amount.

For example, when the partition size is a first partition size, themaximum list size may be a first list size. When the partition size is asecond partition size smaller than the first partition size, the maximumlist size may be a second list size larger than the first list size.

In this way, decoder 200 is capable of selecting an appropriate motionvector from among the large number of motion vector candidates for thesmall partition. On the other hand, there is a possibility that noappropriate motion vector is included in the large number of motionvector candidates for the large partition. Accordingly, decoder 200 iscapable of contributing to the reduction in code amount of the indexindicating the motion vector by using the motion vector candidate listhaving the small maximum list size for the large partition.

For example, when the partition size is a first partition size, themaximum list size may be the first list size. When the partition size isa second partition size smaller than the first partition size, themaximum list size may be a second list size smaller than the first listsize.

In this way, decoder 200 is capable of selecting an appropriate motionvector from among the large number of motion vector candidates for thelarge partition. Accordingly, decoder 200 is capable of simplifying theprocessing and contributing to reduction in code amount of the indexindicating the motion vector by using the motion vector candidate listhaving the small maximum list size for the small partition.

In addition, for example, the maximum list size may be dependent on thepartition shape which is one of a square, a rectangle, or a triangle. Inthis way, decoder 200 is capable of generating an appropriate candidatelist based on the partition shape which is one of a square, a rectangle,or a triangle.

In addition, for example, when the partition shape is a triangle, themaximum list size may be a first list size. When the partition shape isnot a triangle, the maximum list size may be a second list size largerthan the first list size.

In this way, decoder 200 is capable of selecting an appropriate motionvector from among a large number of motion vector candidates for arectangular partition. On the other hand, there is a possibility thatthe number of referable processed partitions is small and the number ofderivable motion vector candidates is small around the triangularpartition. Accordingly, decoder 200 is capable of contributing toreduction in code amount of the index indicating the motion vector byusing the motion vector candidate list having the small maximum listsize for the triangular partition.

In addition, for example, when the partition shape is a square, themaximum list size may be a first list size. When the partition shape isnot a square, the maximum list size may be a second list size largerthan the first list size.

In this way, decoder 200 is capable of selecting an appropriate motionvector from among a large number of motion vector candidates for apartition having a complicated shape. Accordingly, decoder 200 iscapable of simplifying processing and contributing to reduction in codeamount of an index indicating a motion vector by using a motion vectorcandidate list having a small maximum list size for a partition having asimple shape.

In addition, for example, when the maximum list size is the first listsize, circuitry 260 may decode an index using a first number of bits.When the maximum list size is a second list size larger than a firstlist size, circuitry 260 may then decode the index using a second numberof bits larger than the first number of bits. In this way, decoder 200is capable of decoding the index using an appropriate number of bitsbased on the maximum list size.

In addition, for example, the second partition may be a partition thatneighbors the first partition.

In this way, decoder 200 is capable of deriving a candidate for themotion vector for the current partition from a motion vector of apartition that neighbors the current partition. Accordingly, decoder 200is capable of appropriately deriving the candidate for the motion vectorfor the current partition from the motion vector that is assumed to besimilar to the motion vector for the current partition.

[Supplements]

Encoder 100 and decoder 200 according to the above-described embodimentsmay be used respectively as image encoder and an image decoder, or as avideo encoder and a video decoder.

Alternatively, each of encoder 100 and decoder 200 may be used as aprediction device or an inter prediction device. In other words, each ofencoder 100 and decoder 200 may correspond only to inter predictor 126and inter predictor 218, respectively. The other constituent elements ofentropy encoder 110, entropy decoder 202, etc. may be included in one ormore other devices.

Alternatively, at least part of the embodiments may be used as anencoding method and/or a decoding method, as a prediction method, and/oras other methods.

In addition, in the above descriptions, the maximum list size or theorder of candidates in the motion vector candidate list for the motionvector to encode the current partition are dependent on the partitionsize and the partition shape of the current partition.

However, the maximum list size or the order of candidates in the motionvector predictor candidate list for a motion vector predictor to encodethe current partition may be dependent on the partition size or thepartition shape of the current partition. In other words, the motionvector may be replaced by the motion vector predictor. For example, inthis case, a motion vector difference which is a difference between themotion vector and the motion vector predictor is encoded and decoded.

In addition, in each of the above embodiments, each of the constituentelements may be implemented with a dedicated hardware configuration orimplemented by executing a software program suitable for the constituentelement. Each constituent element may be implemented by a programexecuter such as a CPU or a processor reading and executing a softwareprogram which is recorded on a recording medium such as a hard disc or asemiconductor memory.

Specifically, each of encoder 100 and decoder 200 may include processingcircuitry and storage electrically connected to the processing circuitryand accessible from the processing circuitry. For example, theprocessing circuitry corresponds to circuitry 160 or 260, and thestorage corresponds to memory 162 or 262.

The processing circuitry includes at least one of the dedicated hardwareor the program executor, and executes the process using the storage. Inaddition, when the processing circuitry includes the program executor,the storage stores a software program that is executed by the programexecutor.

Here, the software which implements encoder 100, decoder 200, etc.according to each of the above-described embodiments is a program asindicated below.

For example, this program may cause a computer to execute an encodingmethod of encoding a video into a bitstream using a predicted image. Theencoding method includes generating a list which includes a plurality ofcandidates for a first motion vector for a first partition in the video,and in which the plurality of candidates includes a candidate which isderived from a second motion vector of a second partition different fromthe first partition in the video. The list has a maximum list size andan order of the plurality of candidates, and at least one of the maximumlist size or the order of the plurality of candidates is dependent on atleast one of a partition size or a partition shape of the firstpartition. The encoding method includes: selecting the first motionvector from the plurality of candidates included in the list; encodingan index indicating the first motion vector among the plurality ofcandidates in the list into the bitstream based on the maximum listsize; and generating the predicted image for the first partition usingthe first motion vector.

In addition, for example, this program may cause a computer to execute adecoding method of decoding a video from a bitstream using a predictedimage. The decoding method includes generating a list which includes aplurality of candidates for a first motion vector for a first partitionin the video, and in which the plurality of candidates includes acandidate which is derived from a second motion vector of a secondpartition different from the first partition in the video. The listhaving a maximum list size and an order of the plurality of candidates,and at least one of the maximum list size or the order of the pluralityof candidates is dependent on at least one of a partition size or apartition shape of the first partition; decoding an index indicating thefirst motion vector among the plurality of candidates in the list fromthe bitstream based on the maximum list size. The decoding methodincludes selecting the first motion vector from the plurality ofcandidates in the list using the index, and generating the predictedimage for the first partition using the first motion vector.

In addition, each constituent element may be circuitry as describedabove. Circuits may compose circuitry as a whole, or may be separatecircuits. Alternatively, each constituent element may be implemented asa general processor, or may be implemented as a dedicated processor.

In addition, the process that is executed by a particular constituentelement may be executed by another constituent element. In addition, theprocessing execution order may be modified, or a plurality of processesmay be executed in parallel. In addition, an encoder and decoder mayinclude encoder 100 and decoder 200.

The ordinal numbers such as “first” and “second” used in the descriptionmay be arbitrarily changed. In addition, ordinal numbers may bearbitrarily added to constituent elements, etc., or may be removed fromconstituent elements, etc.

Although aspects of encoder 100 and decoder 200 have been describedbased on the embodiments, aspects of encoder 100 and decoder 200 are notlimited to the embodiments. The scope of the aspects of encoder 100 anddecoder 200 may encompass embodiments obtainable by adding, to any ofthese embodiments, various kinds of modifications that a person skilledin the art would arrive at without deviating from the scope of thepresent disclosure and embodiments configurable by arbitrarily combiningconstituent elements in different embodiments.

This embodiment may be performed in combination with at least part ofother aspects of the present disclosure. In addition, part of processingdescribed in each of the flow charts, part of the configuration of eachof the devices, part of each of syntaxes, etc. according to thisembodiment may be combined with one or more other aspects.

Embodiment 2

As described in the above embodiment, each functional block cantypically be realized as an MPU and memory, for example. Moreover,processes performed by each of the functional blocks are typicallyrealized by a program execution unit, such as a processor, reading andexecuting software (a program) recorded on a recording medium such asROM. The software may be distributed via, for example, downloading, andmay be recorded on a recording medium such as semiconductor memory anddistributed. Note that each functional block can, of course, also berealized as hardware (dedicated circuit).

Moreover, the processing described in the embodiment may be realized viaintegrated processing using a single apparatus (system), and,alternatively, may be realized via decentralized processing using aplurality of apparatuses. Moreover, the processor that executes theabove-described program may be a single processor or a plurality ofprocessors. In other words, integrated processing may be performed, and,alternatively, decentralized processing may be performed.

Embodiments of the present disclosure are not limited to the aboveexemplary embodiment: various modifications may be made to the exemplaryembodiments, the results of which are also included within the scope ofthe embodiments of the present disclosure.

Next, application examples of the moving picture encoding method (imageencoding method) and the moving picture decoding method (image decodingmethod) described in the above embodiments and a system that employs thesame will be described. The system is characterized as including animage encoder that employs the image encoding method, an image decoderthat employs the image decoding method, and an image encoder/decoderthat includes both the image encoder and the image decoder. Otherconfigurations included in the system may be modified on a case-by-casebasis.

[Usage Examples]

FIG. 31 illustrates an overall configuration of content providing systemex100 for implementing a content distribution service. The area in whichthe communication service is provided is divided into cells of desiredsizes, and base stations ex106, ex107, ex108, ex109, and ex110, whichare fixed wireless stations, are located in respective cells.

In content providing system ex100, devices including computer ex111,gaming device ex112, camera ex113, home appliance ex114, and smartphoneex115 are connected to internet ex101 via internet service providerex102 or communications network ex104 and base stations ex106 throughex110. Content providing system ex100 may combine and connect anycombination of the above elements. The devices may be directly orindirectly connected together via a telephone network or near fieldcommunication rather than via base stations ex106 through ex110, whichare fixed wireless stations. Moreover, streaming server ex103 isconnected to devices including computer ex111, gaming device ex112,camera ex113, home appliance ex114, and smartphone ex115 via, forexample, internet ex101. Streaming server ex103 is also connected to,for example, a terminal in a hotspot in airplane ex117 via satelliteex116.

Note that instead of base stations ex106 through ex110, wireless accesspoints or hotspots may be used. Streaming server ex103 may be connectedto communications network ex104 directly instead of via internet ex101or internet service provider ex102, and may be connected to airplaneex117 directly instead of via satellite ex116.

Camera ex113 is a device capable of capturing still images and video,such as a digital camera. Smartphone ex115 is a smartphone device,cellular phone, or personal handyphone system (PHS) phone that canoperate under the mobile communications system standards of the typical2G, 3G, 3.9G, and 4G systems, as well as the next-generation 5G system.

Home appliance ex118 is, for example, a refrigerator or a deviceincluded in a home fuel cell cogeneration system.

In content providing system ex100, a terminal including an image and/orvideo capturing function is capable of, for example, live streaming byconnecting to streaming server ex103 via, for example, base stationex106. When live streaming, a terminal (e.g., computer ex111, gamingdevice ex112, camera ex113, home appliance ex114, smartphone ex115, orairplane ex117) performs the encoding processing described in the aboveembodiment on still-image or video content captured by a user via theterminal, multiplexes video data obtained via the encoding and audiodata obtained by encoding audio corresponding to the video, andtransmits the obtained data to streaming server ex103. In other words,the terminal functions as the image encoder according to one aspect ofthe present disclosure.

Streaming server ex103 streams transmitted content data to clients thatrequest the stream. Client examples include computer ex111, gamingdevice ex112, camera ex113, home appliance ex114, smartphone ex115, andterminals inside airplane ex117, which are capable of decoding theabove-described encoded data. Devices that receive the streamed datadecode and reproduce the received data. In other words, the devices eachfunction as the image decoder according to one aspect of the presentdisclosure.

[Decentralized Processing]

Streaming server ex103 may be realized as a plurality of servers orcomputers between which tasks such as the processing, recording, andstreaming of data are divided. For example, streaming server ex103 maybe realized as a content delivery network (CDN) that streams content viaa network connecting multiple edge servers located throughout the world.In a CDN, an edge server physically near the client is dynamicallyassigned to the client. Content is cached and streamed to the edgeserver to reduce load times. In the event of for example, some kind ofan error or a change in connectivity due to, for example, a spike intraffic, it is possible to stream data stably at high speeds since it ispossible to avoid affected parts of the network by, for example,dividing the processing between a plurality of edge servers or switchingthe streaming duties to a different edge server, and continuingstreaming.

Decentralization is not limited to just the division of processing forstreaming; the encoding of the captured data may be divided between andperformed by the terminals, on the server side, or both. In one example,in typical encoding, the processing is performed in two loops. The firstloop is for detecting how complicated the image is on a frame-by-frameor scene-by-scene basis, or detecting the encoding load. The second loopis for processing that maintains image quality and improves encodingefficiency. For example, it is possible to reduce the processing load ofthe terminals and improve the quality and encoding efficiency of thecontent by having the terminals perform the first loop of the encodingand having the server side that received the content perform the secondloop of the encoding. In such a case, upon receipt of a decodingrequest, it is possible for the encoded data resulting from the firstloop performed by one terminal to be received and reproduced on anotherterminal in approximately real time. This makes it possible to realizesmooth, real-time streaming.

In another example, camera ex113 or the like extracts a feature amountfrom an image, compresses data related to the feature amount asmetadata, and transmits the compressed metadata to a server. Forexample, the server determines the significance of an object based onthe feature amount and changes the quantization accuracy accordingly toperform compression suitable for the meaning of the image. Featureamount data is particularly effective in improving the precision andefficiency of motion vector prediction during the second compressionpass performed by the server. Moreover, encoding that has a relativelylow processing load, such as variable length coding (VLC), may behandled by the terminal, and encoding that has a relatively highprocessing load, such as context-adaptive binary arithmetic coding(CABAC), may be handled by the server.

In yet another example, there are instances in which a plurality ofvideos of approximately the same scene are captured by a plurality ofterminals in, for example, a stadium, shopping mall, or factory. In sucha case, for example, the encoding may be decentralized by dividingprocessing tasks between the plurality of terminals that captured thevideos and, if necessary, other terminals that did not capture thevideos and the server, on a per-unit basis. The units may be, forexample, groups of pictures (GOP), pictures, or tiles resulting fromdividing a picture. This makes it possible to reduce load times andachieve streaming that is closer to real-time.

Moreover, since the videos are of approximately the same scene,management and/or instruction may be carried out by the server so thatthe videos captured by the terminals can be cross-referenced. Moreover,the server may receive encoded data from the terminals, change referencerelationship between items of data or correct or replace picturesthemselves, and then perform the encoding. This makes it possible togenerate a stream with increased quality and efficiency for theindividual items of data.

Moreover, the server may stream video data after performing transcodingto convert the encoding format of the video data. For example, theserver may convert the encoding format from MPEG to VP, and may convertH.264 to H.265.

In this way, encoding can be performed by a terminal or one or moreservers. Accordingly, although the device that performs the encoding isreferred to as a “server” or “terminal” in the following description,some or all of the processes performed by the server may be performed bythe terminal, and likewise some or all of the processes performed by theterminal may be performed by the server. This also applies to decodingprocesses.

[3D, Multi-Angle]

In recent years, usage of images or videos combined from images orvideos of different scenes concurrently captured or the same scenecaptured from different angles by a plurality of terminals such ascamera ex113 and/or smartphone ex115 has increased. Videos captured bythe terminals are combined based on, for example, theseparately-obtained relative positional relationship between theterminals, or regions in a video having matching feature points.

In addition to the encoding of two-dimensional moving pictures, theserver may encode a still image based on scene analysis of a movingpicture either automatically or at a point in time specified by theuser, and transmit the encoded still image to a reception terminal.Furthermore, when the server can obtain the relative positionalrelationship between the video capturing terminals, in addition totwo-dimensional moving pictures, the server can generatethree-dimensional geometry of a scene based on video of the same scenecaptured from different angles. Note that the server may separatelyencode three-dimensional data generated from, for example, a pointcloud, and may, based on a result of recognizing or tracking a person orobject using three-dimensional data, select or reconstruct and generatea video to be transmitted to a reception terminal from videos capturedby a plurality of terminals.

This allows the user to enjoy a scene by freely selecting videoscorresponding to the video capturing terminals, and allows the user toenjoy the content obtained by extracting, from three-dimensional datareconstructed from a plurality of images or videos, a video from aselected viewpoint. Furthermore, similar to with video, sound may berecorded from relatively different angles, and the server may multiplex,with the video, audio from a specific angle or space in accordance withthe video, and transmit the result.

In recent years, content that is a composite of the real world and avirtual world, such as virtual reality (VR) and augmented reality (AR)content, has also become popular. In the case of VR images, the servermay create images from the viewpoints of both the left and right eyesand perform encoding that tolerates reference between the two viewpointimages, such as multi-view coding (MVC), and, alternatively, may encodethe images as separate streams without referencing. When the images aredecoded as separate streams, the streams may be synchronized whenreproduced so as to recreate a virtual three-dimensional space inaccordance with the viewpoint of the user.

In the case of AR images, the server superimposes virtual objectinformation existing in a virtual space onto camera informationrepresenting a real-world space, based on a three-dimensional positionor movement from the perspective of the user. The decoder may obtain orstore virtual object information and three-dimensional data, generatetwo-dimensional images based on movement from the perspective of theuser, and then generate superimposed data by seamlessly connecting theimages. Alternatively, the decoder may transmit, to the server, motionfrom the perspective of the user in addition to a request for virtualobject information, and the server may generate superimposed data basedon three-dimensional data stored in the server in accordance with thereceived motion, and encode and stream the generated superimposed datato the decoder. Note that superimposed data includes, in addition to RGBvalues, an α value indicating transparency, and the server sets the avalue for sections other than the object generated fromthree-dimensional data to, for example, 0, and may perform the encodingwhile those sections are transparent. Alternatively, the server may setthe background to a predetermined RGB value, such as a chroma key, andgenerate data in which areas other than the object are set as thebackground.

Decoding of similarly streamed data may be performed by the client(i.e., the terminals), on the server side, or divided therebetween. Inone example, one terminal may transmit a reception request to a server,the requested content may be received and decoded by another terminal,and a decoded signal may be transmitted to a device having a display. Itis possible to reproduce high image quality data by decentralizingprocessing and appropriately selecting content regardless of theprocessing ability of the communications terminal itself. In yet anotherexample, while a TV, for example, is receiving image data that is largein size, a region of a picture, such as a tile obtained by dividing thepicture, may be decoded and displayed on a personal terminal orterminals of a viewer or viewers of the TV. This makes it possible forthe viewers to share a big-picture view as well as for each viewer tocheck his or her assigned area or inspect a region in further detail upclose.

In the future, both indoors and outdoors, in situations in which aplurality of wireless connections are possible over near, mid, and fardistances, it is expected to be able to seamlessly receive content evenwhen switching to data appropriate for the current connection, using astreaming system standard such as MPEG-DASH. With this, the user canswitch between data in real time while freely selecting a decoder ordisplay apparatus including not only his or her own terminal, but also,for example, displays disposed indoors or outdoors. Moreover, based on,for example, information on the position of the user, decoding can beperformed while switching which terminal handles decoding and whichterminal handles the displaying of content. This makes it possible to,while in route to a destination, display, on the wall of a nearbybuilding in which a device capable of displaying content is embedded oron part of the ground, map information while on the move. Moreover, itis also possible to switch the bit rate of the received data based onthe accessibility to the encoded data on a network, such as when encodeddata is cached on a server quickly accessible from the receptionterminal or when encoded data is copied to an edge server in a contentdelivery service.

[Scalable Encoding]

The switching of content will be described with reference to a scalablestream, illustrated in FIG. 32, that is compression coded viaimplementation of the moving picture encoding method described in theabove embodiment. The server may have a configuration in which contentis switched while making use of the temporal and/or spatial scalabilityof a stream, which is achieved by division into and encoding of layers,as illustrated in FIG. 32. Note that there may be a plurality ofindividual streams that are of the same content but different quality.In other words, by determining which layer to decode up to based oninternal factors, such as the processing ability on the decoder side,and external factors, such as communication bandwidth, the decoder sidecan freely switch between low resolution content and high resolutioncontent while decoding. For example, in a case in which the user wantsto continue watching, at home on a device such as a TV connected to theinternet, a video that he or she had been previously watching onsmartphone ex115 while on the move, the device can simply decode thesame stream up to a different layer, which reduces server side load.

Furthermore, in addition to the configuration described above in whichscalability is achieved as a result of the pictures being encoded perlayer and the enhancement layer is above the base layer, the enhancementlayer may include metadata based on, for example, statisticalinformation on the image, and the decoder side may generate high imagequality content by performing super-resolution imaging on a picture inthe base layer based on the metadata. Super-resolution imaging may beimproving the SN ratio while maintaining resolution and/or increasingresolution. Metadata includes information for identifying a linear or anon-linear filter coefficient used in super-resolution processing, orinformation identifying a parameter value in filter processing, machinelearning, or least squares method used in super-resolution processing.

Alternatively, a configuration in which a picture is divided into, forexample, tiles in accordance with the meaning of, for example, an objectin the image, and on the decoder side, only a partial region is decodedby selecting a tile to decode, is also acceptable. Moreover, by storingan attribute about the object (person, car, ball, etc.) and a positionof the object in the video (coordinates in identical images) asmetadata, the decoder side can identify the position of a desired objectbased on the metadata and determine which tile or tiles include thatobject. For example, as illustrated in FIG. 33, metadata is stored usinga data storage structure different from pixel data such as an SEImessage in HEVC. This metadata indicates, for example, the position,size, or color of the main object.

Moreover, metadata may be stored in units of a plurality of pictures,such as stream, sequence, or random access units. With this, the decoderside can obtain, for example, the time at which a specific personappears in the video, and by fitting that with picture unit information,can identify a picture in which the object is present and the positionof the object in the picture.

[Web Page Optimization]

FIG. 34 illustrates an example of a display screen of a web page on, forexample, computer ex111. FIG. 35 illustrates an example of a displayscreen of a web page on, for example, smartphone ex115. As illustratedin FIG. 34 and FIG. 35, a web page may include a plurality of imagelinks which are links to image content, and the appearance of the webpage differs depending on the device used to view the web page. When aplurality of image links are viewable on the screen, until the userexplicitly selects an image link, or until the image link is in theapproximate center of the screen or the entire image link fits in thescreen, the display apparatus (decoder) displays, as the image links,still images included in the content or I pictures, displays video suchas an animated gif using a plurality of still images or I pictures, forexample, or receives only the base layer and decodes and displays thevideo.

When an image link is selected by the user, the display apparatusdecodes giving the highest priority to the base layer. Note that ifthere is information in the HTML code of the web page indicating thatthe content is scalable, the display apparatus may decode up to theenhancement layer. Moreover, in order to guarantee real timereproduction, before a selection is made or when the bandwidth isseverely limited, the display apparatus can reduce delay between thepoint in time at which the leading picture is decoded and the point intime at which the decoded picture is displayed (that is, the delaybetween the start of the decoding of the content to the displaying ofthe content) by decoding and displaying only forward reference pictures(I picture, P picture, forward reference B picture). Moreover, thedisplay apparatus may purposely ignore the reference relationshipbetween pictures and coarsely decode all B and P pictures as forwardreference pictures, and then perform normal decoding as the number ofpictures received over time increases.

[Autonomous Driving]

When transmitting and receiving still image or video data such two- orthree-dimensional map information for autonomous driving or assisteddriving of an automobile, the reception terminal may receive, inaddition to image data belonging to one or more layers, information on,for example, the weather or road construction as metadata, and associatethe metadata with the image data upon decoding. Note that metadata maybe assigned per layer and, alternatively, may simply be multiplexed withthe image data.

In such a case, since the automobile, drone, airplane, etc., includingthe reception terminal is mobile, the reception terminal can seamlesslyreceive and decode while switching between base stations among basestations ex106 through ex110 by transmitting information indicating theposition of the reception terminal upon reception request. Moreover, inaccordance with the selection made by the user, the situation of theuser, or the bandwidth of the connection, the reception terminal candynamically select to what extent the metadata is received or to whatextent the map information, for example, is updated.

With this, in content providing system ex100, the client can receive,decode, and reproduce, in real time, encoded information transmitted bythe user.

[Streaming of Individual Content]

In content providing system ex100, in addition to high image quality,long content distributed by a video distribution entity, unicast ormulticast streaming of low image quality, short content from anindividual is also possible. Moreover, such content from individuals islikely to further increase in popularity. The server may first performediting processing on the content before the encoding processing inorder to refine the individual content. This may be achieved with, forexample, the following configuration.

In real-time while capturing video or image content or after the contenthas been captured and accumulated, the server performs recognitionprocessing based on the raw or encoded data, such as capture errorprocessing, scene search processing, meaning analysis, and/or objectdetection processing. Then, based on the result of the recognitionprocessing, the server-either when prompted or automatically-edits thecontent, examples of which include: correction such as focus and/ormotion blur correction; removing low-priority scenes such as scenes thatare low in brightness compared to other pictures or out of focus; objectedge adjustment; and color tone adjustment. The server encodes theedited data based on the result of the editing. It is known thatexcessively long videos tend to receive fewer views. Accordingly, inorder to keep the content within a specific length that scales with thelength of the original video, the server may, in addition to thelow-priority scenes described above, automatically clip out scenes withlow movement based on an image processing result. Alternatively, theserver may generate and encode a video digest based on a result of ananalysis of the meaning of a scene.

Note that there are instances in which individual content may includecontent that infringes a copyright, moral right, portrait rights, etc.Such an instance may lead to an unfavorable situation for the creator,such as when content is shared beyond the scope intended by the creator.Accordingly, before encoding, the server may, for example, edit imagesso as to blur faces of people in the periphery of the screen or blur theinside of a house, for example. Moreover, the server may be configuredto recognize the faces of people other than a registered person inimages to be encoded, and when such faces appear in an image, forexample, apply a mosaic filter to the face of the person. Alternatively,as pre- or post-processing for encoding, the user may specify, forcopyright reasons, a region of an image including a person or a regionof the background be processed, and the server may process the specifiedregion by, for example, replacing the region with a different image orblurring the region. If the region includes a person, the person may betracked in the moving picture the head region may be replaced withanother image as the person moves.

Moreover, since there is a demand for real-time viewing of contentproduced by individuals, which tends to be small in data size, thedecoder first receives the base layer as the highest priority andperforms decoding and reproduction, although this may differ dependingon bandwidth. When the content is reproduced two or more times, such aswhen the decoder receives the enhancement layer during decoding andreproduction of the base layer and loops the reproduction, the decodermay reproduce a high image quality video including the enhancementlayer. If the stream is encoded using such scalable encoding, the videomay be low quality when in an unselected state or at the start of thevideo, but it can offer an experience in which the image quality of thestream progressively increases in an intelligent manner. This is notlimited to just scalable encoding; the same experience can be offered byconfiguring a single stream from a low quality stream reproduced for thefirst time and a second stream encoded using the first stream as areference.

[Other Usage Examples]

The encoding and decoding may be performed by LSI ex500, which istypically included in each terminal. LSI ex500 may be configured of asingle chip or a plurality of chips. Software for encoding and decodingmoving pictures may be integrated into some type of a recording medium(such as a CD-ROM, a flexible disk, or a hard disk) that is readable by,for example, computer ex111, and the encoding and decoding may beperformed using the software. Furthermore, when smartphone ex115 isequipped with a camera, the video data obtained by the camera may betransmitted. In this case, the video data is coded by LSI ex500 includedin smartphone ex115.

Note that LSI ex500 may be configured to download and activate anapplication. In such a case, the terminal first determines whether it iscompatible with the scheme used to encode the content or whether it iscapable of executing a specific service. When the terminal is notcompatible with the encoding scheme of the content or when the terminalis not capable of executing a specific service, the terminal firstdownloads a codec or application software then obtains and reproducesthe content.

Aside from the example of content providing system ex100 that usesinternet ex101, at least the moving picture encoder (image encoder) orthe moving picture decoder (image decoder) described in the aboveembodiment may be implemented in a digital broadcasting system. The sameencoding processing and decoding processing may be applied to transmitand receive broadcast radio waves superimposed with multiplexed audioand video data using, for example, a satellite, even though this isgeared toward multicast whereas unicast is easier with content providingsystem ex100.

[Hardware Configuration]

FIG. 36 illustrates smartphone ex115. FIG. 37 illustrates aconfiguration example of smartphone ex115. Smartphone ex115 includesantenna ex450 for transmitting and receiving radio waves to and frombase station ex110, camera ex465 capable of capturing video and stillimages, and display ex458 that displays decoded data, such as videocaptured by camera ex465 and video received by antenna ex450. Smartphoneex115 further includes user interface ex466 such as a touch panel, audiooutput unit ex457 such as a speaker for outputting speech or otheraudio, audio input unit ex456 such as a microphone for audio input,memory ex467 capable of storing decoded data such as captured video orstill images, recorded audio, received video or still images, and mail,as well as decoded data, and slot ex464 which is an interface for SIMex468 for authorizing access to a network and various data. Note thatexternal memory may be used instead of memory ex467.

Moreover, main controller ex460 which comprehensively controls displayex458 and user interface ex466, power supply circuit ex461, userinterface input controller ex462, video signal processor ex455, camerainterface ex463, display controller ex459, modulator/demodulator ex452,multiplexer/demultiplexer ex453, audio signal processor ex454, slotex464, and memory ex467 are connected via bus ex470.

When the user turns the power button of power supply circuit ex461 on,smartphone ex115 is powered on into an operable state by each componentbeing supplied with power from a battery pack.

Smartphone ex115 performs processing for, for example, calling and datatransmission, based on control performed by main controller ex460, whichincludes a CPU, ROM, and RAM. When making calls, an audio signalrecorded by audio input unit ex456 is converted into a digital audiosignal by audio signal processor ex454, and this is applied with spreadspectrum processing by modulator/demodulator ex452 and digital-analogconversion and frequency conversion processing by transmitter/receiverex451, and then transmitted via antenna ex450. The received data isamplified, frequency converted, and analog-digital converted, inversespread spectrum processed by modulator/demodulator ex452, converted intoan analog audio signal by audio signal processor ex454, and then outputfrom audio output unit ex457. In data transmission mode, text,still-image, or video data is transmitted by main controller ex460 viauser interface input controller ex462 as a result of operation of forexample, user interface ex466 of the main body, and similar transmissionand reception processing is performed. In data transmission mode, whensending a video, still image, or video and audio, video signal processorex455 compression encodes, via the moving picture encoding methoddescribed in the above embodiment, a video signal stored in memory ex467or a video signal input from camera ex465, and transmits the encodedvideo data to multiplexer/demultiplexer ex453. Moreover, audio signalprocessor ex454 encodes an audio signal recorded by audio input unitex456 while camera ex465 is capturing, for example, a video or stillimage, and transmits the encoded audio data to multiplexer/demultiplexerex453. Multiplexer/demultiplexer ex453 multiplexes the encoded videodata and encoded audio data using a predetermined scheme, modulates andconverts the data using modulator/demodulator (modulator/demodulatorcircuit) ex452 and transmitter/receiver ex451, and transmits the resultvia antenna ex450.

When video appended in an email or a chat, or a video linked from a webpage, for example, is received, in order to decode the multiplexed datareceived via antenna ex450, multiplexer/demultiplexer ex453demultiplexes the multiplexed data to divide the multiplexed data into abitstream of video data and a bitstream of audio data, supplies theencoded video data to video signal processor ex455 via synchronous busex470, and supplies the encoded audio data to audio signal processorex454 via synchronous bus ex470. Video signal processor ex455 decodesthe video signal using a moving picture decoding method corresponding tothe moving picture encoding method described in the above embodiment,and video or a still image included in the linked moving picture file isdisplayed on display ex458 via display controller ex459. Moreover, audiosignal processor ex454 decodes the audio signal and outputs audio fromaudio output unit ex457. Note that since real-time streaming is becomingmore and more popular, there are instances in which reproduction of theaudio may be socially inappropriate depending on the user's environment.Accordingly, as an initial value, a configuration in which only videodata is reproduced. i.e., the audio signal is not reproduced, ispreferable. Audio may be synchronized and reproduced only when an input,such as when the user clicks video data, is received.

Although smartphone ex115 was used in the above example, threeimplementations are conceivable: a transceiver terminal including bothan encoder and a decoder; a transmitter terminal including only anencoder; and a receiver terminal including only a decoder. Further, inthe description of the digital broadcasting system, an example is givenin which multiplexed data obtained as a result of video data beingmultiplexed with, for example, audio data, is received or transmitted,but the multiplexed data may be video data multiplexed with data otherthan audio data, such as text data related to the video. Moreover, thevideo data itself rather than multiplexed data maybe received ortransmitted.

Although main controller ex460 including a CPU is described ascontrolling the encoding or decoding processes, terminals often includeGPUs. Accordingly a configuration is acceptable in which a large area isprocessed at once by making use of the performance ability of the GPUvia memory shared by the CPU and GPU or memory including an address thatis managed so as to allow common usage by the CPU and GPU. This makes itpossible to shorten encoding time, maintain the real-time nature of thestream, and reduce delay. In particular, processing relating to motionestimation, deblocking filtering, sample adaptive offset (SAO), andtransformation/quantization can be effectively carried out by the GPUinstead of the CPU in units of, for example pictures, all at once.

Although only some exemplary embodiments of the present disclosure havebeen described in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of the present disclosure. Accordingly, all suchmodifications are intended to be included within the scope of thepresent disclosure.

INDUSTRIAL APPLICABILITY

The present disclosure is applicable to, for example, televisionreceivers, digital video recorders, car navigation systems, mobilephones, digital cameras, digital video cameras, teleconferencingsystems, electronic mirrors, etc.

What is claimed is:
 1. An encoder which encodes a video into a bitstreamusing a predicted image, the encoder comprising: circuitry; and memory,wherein, using the memory, the circuitry: derives a maximum number basedon a partition shape of a first partition in the video, the maximumnumber being a first number when the partition shape is a square or arectangle, and the maximum number being a second number different fromthe first number when the partition shape is a non-square and anon-rectangle; generates a motion vector candidate list including aplurality of candidates equal to the derived maximum number, theplurality of candidates being for a first motion vector for the firstpartition, and the plurality of candidates including a candidate whichis derived from a second motion vector of a second partition in thevideo different from the first partition; selects the first motionvector from the plurality of candidates included in the motion vectorcandidate list; encodes an index indicating the first motion vectoramong the plurality of candidates in the motion vector candidate listinto the bitstream based on the maximum number; and generates thepredicted image for the first partition using the first motion vector.2. An encoding method of encoding a video into a bitstream using apredicted image, the encoding method comprising: deriving a maximumnumber based on a partition shape of a first partition in the video, themaximum number being a first number when the partition shape is a squareor a rectangle, and the maximum number being a second number differentfrom the first number when the partition shape is a non-square and anon-rectangle; generating a motion vector candidate list including aplurality of candidates equal to the derived maximum number, theplurality of candidates being for a first motion vector for the firstpartition, and the plurality of candidates including a candidate whichis derived from a second motion vector of a second partition in thevideo different from the first partition; selecting the first motionvector from the plurality of candidates included in the motion vectorcandidate list; encoding an index indicating the first motion vectoramong the plurality of candidates in the motion vector candidate listinto the bitstream based on the maximum number; and generating thepredicted image for the first partition using the first motion vector.